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	$233.29	8.759%	$253.7239	$253.72	$253.70	$253.70
Purchase #2	$50.56	5.411%	$53.2958	$53.30	$53.30	$53.30
Purchase #3	$229.68	5.759%	$242.9073	$242.91	$242.90	$242.90
Purchase #4	$75.48	5.379%	$79.5401	$79.54	$79.55	$79.50
Purchase #5	$49.32	9.816%	$54.1613	$54.16	$54.15	$54.20
Purchase #6	$202.71	12.551%	$228.1521	$228.15	$228.15	$228.20
Purchase #7	$104.38	6.715%	$111.3891	$111.39	$111.40	$111.40
7 purchase totals =	$945.42		$1,023.1696	$1,023.17	$1,023.15	$1,023.20