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	$160.31	3.672%	$166.1966	$166.20	$166.20	$166.20
Purchase #2	$86.54	8.493%	$93.8898	$93.89	$93.90	$93.90
Purchase #3	$83.44	7.766%	$89.92	$89.92	$89.90	$89.90
Purchase #4	$245.31	10.513%	$271.0994	$271.10	$271.10	$271.10
Purchase #5	$77.48	10.816%	$85.8602	$85.86	$85.85	$85.90
Purchase #6	$99.74	13.647%	$113.3515	$113.35	$113.35	$113.40
Purchase #7	$193.74	6.529%	$206.3893	$206.39	$206.40	$206.40
7 purchase totals =	$946.56		$1,026.7068	$1,026.71	$1,026.70	$1,026.80