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	$86.80	3.262%	$89.6314	$89.63	$89.65	$89.60
Purchase #2	$89.70	13.140%	$101.4866	$101.49	$101.50	$101.50
Purchase #3	$206.45	5.851%	$218.5294	$218.53	$218.55	$218.50
Purchase #4	$181.29	7.723%	$195.291	$195.29	$195.30	$195.30
Purchase #5	$243.44	9.323%	$266.1359	$266.14	$266.15	$266.10
Purchase #6	$37.75	12.417%	$42.4374	$42.44	$42.45	$42.40
Purchase #7	$188.52	3.616%	$195.3369	$195.34	$195.35	$195.30
7 purchase totals =	$1,033.95		$1,108.8486	$1,108.86	$1,108.95	$1,108.70