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	$100.44	11.281%	$111.7706	$111.77	$111.75	$111.80
Purchase #2	$19.35	13.619%	$21.9853	$21.99	$22.00	$22.00
Purchase #3	$131.76	12.273%	$147.9309	$147.93	$147.95	$147.90
Purchase #4	$212.69	4.740%	$222.7715	$222.77	$222.75	$222.80
Purchase #5	$102.53	9.752%	$112.5287	$112.53	$112.55	$112.50
Purchase #6	$18.92	13.171%	$21.412	$21.41	$21.40	$21.40
Purchase #7	$188.51	11.230%	$209.6797	$209.68	$209.70	$209.70
7 purchase totals =	$774.20		$848.0787	$848.08	$848.10	$848.10