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	$226.55	10.539%	$250.4261	$250.43	$250.45	$250.40
Purchase #2	$43.81	9.286%	$47.8782	$47.88	$47.90	$47.90
Purchase #3	$68.90	5.854%	$72.9334	$72.93	$72.95	$72.90
Purchase #4	$56.52	9.111%	$61.6695	$61.67	$61.65	$61.70
Purchase #5	$103.42	7.651%	$111.3327	$111.33	$111.35	$111.30
Purchase #6	$65.67	4.662%	$68.7315	$68.73	$68.75	$68.70
Purchase #7	$165.47	9.780%	$181.653	$181.65	$181.65	$181.70
7 purchase totals =	$730.34		$794.6244	$794.62	$794.70	$794.60