Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$91.49	11.488%	$102.0004	$102.00	$102.00	$102.00
Purchase #2	$199.54	7.255%	$214.0166	$214.02	$214.00	$214.00
Purchase #3	$125.38	4.766%	$131.3556	$131.36	$131.35	$131.40
Purchase #4	$137.82	5.700%	$145.6757	$145.68	$145.70	$145.70
Purchase #5	$245.37	10.736%	$271.7129	$271.71	$271.70	$271.70
Purchase #6	$91.86	9.130%	$100.2468	$100.25	$100.25	$100.20
Purchase #7	$165.92	12.870%	$187.2739	$187.27	$187.25	$187.30
7 purchase totals =	$1,057.38		$1,152.2819	$1,152.29	$1,152.25	$1,152.30