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	$167.78	12.258%	$188.3465	$188.35	$188.35	$188.30
Purchase #2	$130.63	12.656%	$147.1625	$147.16	$147.15	$147.20
Purchase #3	$101.66	9.410%	$111.2262	$111.23	$111.25	$111.20
Purchase #4	$147.70	4.620%	$154.5237	$154.52	$154.50	$154.50
Purchase #5	$66.75	8.399%	$72.3563	$72.36	$72.35	$72.40
Purchase #6	$167.50	10.290%	$184.7358	$184.74	$184.75	$184.70
Purchase #7	$95.64	9.424%	$104.6531	$104.65	$104.65	$104.70
7 purchase totals =	$877.66		$963.0041	$963.01	$963.00	$963.00