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	$141.80	10.485%	$156.6677	$156.67	$156.65	$156.70
Purchase #2	$85.25	3.663%	$88.3727	$88.37	$88.35	$88.40
Purchase #3	$234.69	4.255%	$244.6761	$244.68	$244.70	$244.70
Purchase #4	$239.85	5.755%	$253.6534	$253.65	$253.65	$253.70
Purchase #5	$90.37	6.630%	$96.3615	$96.36	$96.35	$96.40
Purchase #6	$80.25	11.391%	$89.3913	$89.39	$89.40	$89.40
Purchase #7	$56.52	4.592%	$59.1154	$59.12	$59.10	$59.10
7 purchase totals =	$928.73		$988.2381	$988.24	$988.20	$988.40