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	$66.65	9.637%	$73.0731	$73.07	$73.05	$73.10
Purchase #2	$197.92	7.424%	$212.6136	$212.61	$212.60	$212.60
Purchase #3	$19.37	12.131%	$21.7198	$21.72	$21.70	$21.70
Purchase #4	$130.98	6.586%	$139.6063	$139.61	$139.60	$139.60
Purchase #5	$92.91	3.479%	$96.1423	$96.14	$96.15	$96.10
Purchase #6	$108.73	3.472%	$112.5051	$112.51	$112.50	$112.50
Purchase #7	$78.68	5.591%	$83.079	$83.08	$83.10	$83.10
7 purchase totals =	$695.24		$738.7392	$738.74	$738.70	$738.70