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	$75.57	10.848%	$83.7678	$83.77	$83.75	$83.80
Purchase #2	$212.81	10.834%	$235.8658	$235.87	$235.85	$235.90
Purchase #3	$56.65	3.849%	$58.8305	$58.83	$58.85	$58.80
Purchase #4	$208.54	7.374%	$223.9177	$223.92	$223.90	$223.90
Purchase #5	$54.91	7.479%	$59.0167	$59.02	$59.00	$59.00
Purchase #6	$101.28	9.830%	$111.2358	$111.24	$111.25	$111.20
Purchase #7	$216.79	13.317%	$245.6599	$245.66	$245.65	$245.70
7 purchase totals =	$926.55		$1,018.2942	$1,018.31	$1,018.25	$1,018.30