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	$165.29	4.137%	$172.128	$172.13	$172.15	$172.10
Purchase #2	$120.89	5.415%	$127.4362	$127.44	$127.45	$127.40
Purchase #3	$80.63	7.491%	$86.67	$86.67	$86.65	$86.70
Purchase #4	$50.47	5.556%	$53.2741	$53.27	$53.25	$53.30
Purchase #5	$227.44	7.649%	$244.8369	$244.84	$244.85	$244.80
Purchase #6	$204.60	9.230%	$223.4846	$223.48	$223.50	$223.50
Purchase #7	$162.46	5.502%	$171.3985	$171.40	$171.40	$171.40
7 purchase totals =	$1,011.78		$1,079.2283	$1,079.23	$1,079.25	$1,079.20