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	$88.77	4.120%	$92.4273	$92.43	$92.45	$92.40
Purchase #2	$128.51	11.540%	$143.3401	$143.34	$143.35	$143.30
Purchase #3	$234.70	7.788%	$252.9784	$252.98	$253.00	$253.00
Purchase #4	$177.61	4.381%	$185.3911	$185.39	$185.40	$185.40
Purchase #5	$39.90	6.573%	$42.5226	$42.52	$42.50	$42.50
Purchase #6	$214.27	9.755%	$235.172	$235.17	$235.15	$235.20
Purchase #7	$58.72	9.319%	$64.1921	$64.19	$64.20	$64.20
7 purchase totals =	$942.48		$1,016.0236	$1,016.02	$1,016.05	$1,016.00