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	$198.27	12.828%	$223.7041	$223.70	$223.70	$223.70
Purchase #2	$82.92	8.681%	$90.1183	$90.12	$90.10	$90.10
Purchase #3	$72.55	7.298%	$77.8447	$77.84	$77.85	$77.80
Purchase #4	$89.69	3.601%	$92.9197	$92.92	$92.90	$92.90
Purchase #5	$237.41	9.536%	$260.0494	$260.05	$260.05	$260.00
Purchase #6	$153.76	6.753%	$164.1434	$164.14	$164.15	$164.10
Purchase #7	$133.80	6.393%	$142.3538	$142.35	$142.35	$142.40
7 purchase totals =	$968.40		$1,051.1334	$1,051.12	$1,051.10	$1,051.00