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	$170.45	11.416%	$189.9086	$189.91	$189.90	$189.90
Purchase #2	$46.87	4.727%	$49.0855	$49.09	$49.10	$49.10
Purchase #3	$175.78	11.661%	$196.2777	$196.28	$196.30	$196.30
Purchase #4	$196.62	3.642%	$203.7809	$203.78	$203.80	$203.80
Purchase #5	$124.96	13.172%	$141.4197	$141.42	$141.40	$141.40
Purchase #6	$106.69	4.192%	$111.1624	$111.16	$111.15	$111.20
Purchase #7	$173.45	6.272%	$184.3288	$184.33	$184.35	$184.30
7 purchase totals =	$994.82		$1,075.9636	$1,075.97	$1,076.00	$1,076.00