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	$144.62	9.741%	$158.7074	$158.71	$158.70	$158.70
Purchase #2	$84.72	6.771%	$90.4564	$90.46	$90.45	$90.50
Purchase #3	$54.70	6.279%	$58.1346	$58.13	$58.15	$58.10
Purchase #4	$233.62	7.246%	$250.5481	$250.55	$250.55	$250.50
Purchase #5	$111.74	4.873%	$117.1851	$117.19	$117.20	$117.20
Purchase #6	$72.56	12.383%	$81.5451	$81.55	$81.55	$81.50
Purchase #7	$59.56	6.165%	$63.2319	$63.23	$63.25	$63.20
7 purchase totals =	$761.52		$819.8086	$819.82	$819.85	$819.70