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	$174.41	3.837%	$181.1021	$181.10	$181.10	$181.10
Purchase #2	$216.42	4.399%	$225.9403	$225.94	$225.95	$225.90
Purchase #3	$93.52	10.399%	$103.2451	$103.25	$103.25	$103.20
Purchase #4	$68.43	3.833%	$71.0529	$71.05	$71.05	$71.10
Purchase #5	$127.44	7.714%	$137.2707	$137.27	$137.25	$137.30
Purchase #6	$240.71	11.231%	$267.7441	$267.74	$267.75	$267.70
Purchase #7	$141.83	12.242%	$159.1928	$159.19	$159.20	$159.20
7 purchase totals =	$1,062.76		$1,145.5480	$1,145.54	$1,145.55	$1,145.50