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	$243.40	4.782%	$255.0394	$255.04	$255.05	$255.00
Purchase #2	$190.30	3.206%	$196.401	$196.40	$196.40	$196.40
Purchase #3	$63.29	7.685%	$68.1538	$68.15	$68.15	$68.20
Purchase #4	$184.55	7.123%	$197.6955	$197.70	$197.70	$197.70
Purchase #5	$78.92	13.613%	$89.6634	$89.66	$89.65	$89.70
Purchase #6	$141.25	7.209%	$151.4327	$151.43	$151.45	$151.40
Purchase #7	$99.31	10.828%	$110.0633	$110.06	$110.05	$110.10
7 purchase totals =	$1,001.02		$1,068.4491	$1,068.44	$1,068.45	$1,068.50