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	$85.39	5.685%	$90.2444	$90.24	$90.25	$90.20
Purchase #2	$7.55	3.580%	$7.8203	$7.82	$7.80	$7.80
Purchase #3	$170.44	6.490%	$181.5016	$181.50	$181.50	$181.50
Purchase #4	$248.87	3.745%	$258.1902	$258.19	$258.20	$258.20
Purchase #5	$148.91	11.122%	$165.4718	$165.47	$165.45	$165.50
Purchase #6	$90.78	10.676%	$100.4717	$100.47	$100.45	$100.50
Purchase #7	$186.76	13.690%	$212.3274	$212.33	$212.35	$212.30
7 purchase totals =	$938.70		$1,016.0274	$1,016.02	$1,016.00	$1,016.00