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	$174.76	5.156%	$183.7706	$183.77	$183.75	$183.80
Purchase #2	$124.67	4.149%	$129.8426	$129.84	$129.85	$129.80
Purchase #3	$166.56	3.825%	$172.9309	$172.93	$172.95	$172.90
Purchase #4	$214.98	9.727%	$235.8911	$235.89	$235.90	$235.90
Purchase #5	$54.35	12.747%	$61.278	$61.28	$61.30	$61.30
Purchase #6	$217.73	5.588%	$229.8968	$229.90	$229.90	$229.90
Purchase #7	$67.80	7.448%	$72.8497	$72.85	$72.85	$72.80
7 purchase totals =	$1,020.85		$1,086.4597	$1,086.46	$1,086.50	$1,086.40