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	$245.83	8.303%	$266.2413	$266.24	$266.25	$266.20
Purchase #2	$220.72	13.511%	$250.5415	$250.54	$250.55	$250.50
Purchase #3	$116.71	12.137%	$130.8751	$130.88	$130.90	$130.90
Purchase #4	$53.44	10.607%	$59.1084	$59.11	$59.10	$59.10
Purchase #5	$48.89	8.707%	$53.1469	$53.15	$53.15	$53.10
Purchase #6	$247.77	13.688%	$281.6848	$281.68	$281.70	$281.70
Purchase #7	$68.84	11.278%	$76.6038	$76.60	$76.60	$76.60
7 purchase totals =	$1,002.20		$1,118.2018	$1,118.20	$1,118.25	$1,118.10