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	$221.39	8.255%	$239.6657	$239.67	$239.65	$239.70
Purchase #2	$135.83	7.241%	$145.6655	$145.67	$145.65	$145.70
Purchase #3	$88.86	7.715%	$95.7155	$95.72	$95.70	$95.70
Purchase #4	$78.65	13.539%	$89.2984	$89.30	$89.30	$89.30
Purchase #5	$7.39	11.571%	$8.2451	$8.25	$8.25	$8.20
Purchase #6	$242.39	10.758%	$268.4663	$268.47	$268.45	$268.50
Purchase #7	$209.53	13.743%	$238.3257	$238.33	$238.35	$238.30
7 purchase totals =	$984.04		$1,085.3822	$1,085.41	$1,085.35	$1,085.40