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	$75.66	8.736%	$82.2697	$82.27	$82.25	$82.30
Purchase #2	$201.89	6.849%	$215.7174	$215.72	$215.70	$215.70
Purchase #3	$83.98	12.415%	$94.4061	$94.41	$94.40	$94.40
Purchase #4	$150.41	3.324%	$155.4096	$155.41	$155.40	$155.40
Purchase #5	$118.90	12.216%	$133.4248	$133.42	$133.40	$133.40
Purchase #6	$178.46	7.320%	$191.5233	$191.52	$191.50	$191.50
Purchase #7	$185.42	5.569%	$195.746	$195.75	$195.75	$195.70
7 purchase totals =	$994.72		$1,068.4969	$1,068.50	$1,068.40	$1,068.40