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	$72.65	13.795%	$82.6721	$82.67	$82.65	$82.70
Purchase #2	$97.64	5.776%	$103.2797	$103.28	$103.30	$103.30
Purchase #3	$195.42	8.729%	$212.4782	$212.48	$212.50	$212.50
Purchase #4	$94.34	6.794%	$100.7495	$100.75	$100.75	$100.70
Purchase #5	$166.59	11.138%	$185.1448	$185.14	$185.15	$185.10
Purchase #6	$240.28	13.422%	$272.5304	$272.53	$272.55	$272.50
Purchase #7	$241.95	3.621%	$250.711	$250.71	$250.70	$250.70
7 purchase totals =	$1,108.87		$1,207.5657	$1,207.56	$1,207.60	$1,207.50