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	$190.72	5.191%	$200.6203	$200.62	$200.60	$200.60
Purchase #2	$33.52	7.305%	$35.9686	$35.97	$35.95	$36.00
Purchase #3	$247.74	8.217%	$268.0968	$268.10	$268.10	$268.10
Purchase #4	$36.82	4.171%	$38.3558	$38.36	$38.35	$38.40
Purchase #5	$83.46	5.838%	$88.3324	$88.33	$88.35	$88.30
Purchase #6	$129.27	10.443%	$142.7697	$142.77	$142.75	$142.80
Purchase #7	$42.89	7.543%	$46.1252	$46.13	$46.15	$46.10
7 purchase totals =	$764.42		$820.2688	$820.28	$820.25	$820.30