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	$48.98	5.264%	$51.5583	$51.56	$51.55	$51.60
Purchase #2	$81.31	11.592%	$90.7355	$90.74	$90.75	$90.70
Purchase #3	$86.54	3.731%	$89.7688	$89.77	$89.75	$89.80
Purchase #4	$184.62	9.753%	$202.626	$202.63	$202.65	$202.60
Purchase #5	$54.35	12.201%	$60.9812	$60.98	$61.00	$61.00
Purchase #6	$154.42	3.295%	$159.5081	$159.51	$159.50	$159.50
Purchase #7	$81.53	11.317%	$90.7568	$90.76	$90.75	$90.80
7 purchase totals =	$691.75		$745.9347	$745.95	$745.95	$746.00