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	$186.93	7.321%	$200.6151	$200.62	$200.60	$200.60
Purchase #2	$89.76	10.558%	$99.2369	$99.24	$99.25	$99.20
Purchase #3	$236.42	13.572%	$268.5069	$268.51	$268.50	$268.50
Purchase #4	$61.58	12.662%	$69.3773	$69.38	$69.40	$69.40
Purchase #5	$84.30	5.731%	$89.1312	$89.13	$89.15	$89.10
Purchase #6	$19.59	13.617%	$22.2576	$22.26	$22.25	$22.30
Purchase #7	$171.97	7.318%	$184.5548	$184.55	$184.55	$184.60
7 purchase totals =	$850.55		$933.6798	$933.69	$933.70	$933.70