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	$214.30	10.213%	$236.1865	$236.19	$236.20	$236.20
Purchase #2	$72.91	13.692%	$82.8928	$82.89	$82.90	$82.90
Purchase #3	$209.63	4.404%	$218.8621	$218.86	$218.85	$218.90
Purchase #4	$88.98	11.768%	$99.4512	$99.45	$99.45	$99.50
Purchase #5	$19.80	5.318%	$20.853	$20.85	$20.85	$20.90
Purchase #6	$228.32	12.816%	$257.5815	$257.58	$257.60	$257.60
Purchase #7	$157.64	5.135%	$165.7348	$165.73	$165.75	$165.70
7 purchase totals =	$991.58		$1,081.5619	$1,081.55	$1,081.60	$1,081.70