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	$202.58	3.582%	$209.8364	$209.84	$209.85	$209.80
Purchase #2	$115.35	12.673%	$129.9683	$129.97	$129.95	$130.00
Purchase #3	$162.57	5.660%	$171.7715	$171.77	$171.75	$171.80
Purchase #4	$10.35	10.820%	$11.4699	$11.47	$11.45	$11.50
Purchase #5	$223.32	7.722%	$240.5648	$240.56	$240.55	$240.60
Purchase #6	$89.91	11.827%	$100.5437	$100.54	$100.55	$100.50
Purchase #7	$168.73	6.327%	$179.4055	$179.41	$179.40	$179.40
7 purchase totals =	$972.81		$1,043.5601	$1,043.56	$1,043.50	$1,043.60