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	$93.94	10.363%	$103.675	$103.68	$103.70	$103.70
Purchase #2	$67.65	7.258%	$72.56	$72.56	$72.55	$72.60
Purchase #3	$218.28	4.627%	$228.3798	$228.38	$228.40	$228.40
Purchase #4	$48.62	11.574%	$54.2473	$54.25	$54.25	$54.20
Purchase #5	$181.74	13.427%	$206.1422	$206.14	$206.15	$206.10
Purchase #6	$176.37	11.399%	$196.4744	$196.47	$196.45	$196.50
Purchase #7	$18.34	6.232%	$19.4829	$19.48	$19.50	$19.50
7 purchase totals =	$804.94		$880.9616	$880.96	$881.00	$881.00