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	$78.90	11.646%	$88.0887	$88.09	$88.10	$88.10
Purchase #2	$103.67	5.209%	$109.0702	$109.07	$109.05	$109.10
Purchase #3	$22.33	13.376%	$25.3169	$25.32	$25.30	$25.30
Purchase #4	$48.52	7.862%	$52.3346	$52.33	$52.35	$52.30
Purchase #5	$96.79	7.111%	$103.6727	$103.67	$103.65	$103.70
Purchase #6	$176.92	4.142%	$184.248	$184.25	$184.25	$184.20
Purchase #7	$158.32	4.368%	$165.2354	$165.24	$165.25	$165.20
7 purchase totals =	$685.45		$727.9665	$727.97	$727.95	$727.90