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	$62.71	5.525%	$66.1747	$66.17	$66.15	$66.20
Purchase #2	$96.32	12.225%	$108.0951	$108.10	$108.10	$108.10
Purchase #3	$97.51	13.149%	$110.3316	$110.33	$110.35	$110.30
Purchase #4	$244.41	10.111%	$269.1223	$269.12	$269.10	$269.10
Purchase #5	$139.44	9.483%	$152.6631	$152.66	$152.65	$152.70
Purchase #6	$178.46	11.574%	$199.115	$199.12	$199.10	$199.10
Purchase #7	$105.89	5.851%	$112.0856	$112.09	$112.10	$112.10
7 purchase totals =	$924.74		$1,017.5874	$1,017.59	$1,017.55	$1,017.60