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	$178.57	9.108%	$194.8342	$194.83	$194.85	$194.80
Purchase #2	$85.25	8.550%	$92.5389	$92.54	$92.55	$92.50
Purchase #3	$222.47	12.568%	$250.43	$250.43	$250.45	$250.40
Purchase #4	$131.39	8.795%	$142.9458	$142.95	$142.95	$142.90
Purchase #5	$21.30	5.744%	$22.5235	$22.52	$22.50	$22.50
Purchase #6	$225.25	7.770%	$242.7519	$242.75	$242.75	$242.80
Purchase #7	$203.91	9.365%	$223.0062	$223.01	$223.00	$223.00
7 purchase totals =	$1,068.14		$1,169.0305	$1,169.03	$1,169.05	$1,168.90