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	$33.94	3.319%	$35.0665	$35.07	$35.05	$35.10
Purchase #2	$33.45	8.546%	$36.3086	$36.31	$36.30	$36.30
Purchase #3	$215.94	12.683%	$243.3277	$243.33	$243.35	$243.30
Purchase #4	$29.88	9.559%	$32.7362	$32.74	$32.75	$32.70
Purchase #5	$80.89	6.833%	$86.4172	$86.42	$86.40	$86.40
Purchase #6	$56.33	10.109%	$62.0244	$62.02	$62.00	$62.00
Purchase #7	$96.40	4.662%	$100.8942	$100.89	$100.90	$100.90
7 purchase totals =	$546.83		$596.7748	$596.78	$596.75	$596.70