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	$233.59	13.576%	$265.3022	$265.30	$265.30	$265.30
Purchase #2	$125.44	4.289%	$130.8201	$130.82	$130.80	$130.80
Purchase #3	$193.26	8.209%	$209.1247	$209.12	$209.10	$209.10
Purchase #4	$85.72	4.704%	$89.7523	$89.75	$89.75	$89.80
Purchase #5	$75.34	13.248%	$85.321	$85.32	$85.30	$85.30
Purchase #6	$114.36	4.332%	$119.3141	$119.31	$119.30	$119.30
Purchase #7	$147.31	5.107%	$154.8331	$154.83	$154.85	$154.80
7 purchase totals =	$975.02		$1,054.4675	$1,054.45	$1,054.40	$1,054.40