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	$165.40	8.656%	$179.717	$179.72	$179.70	$179.70
Purchase #2	$143.37	6.260%	$152.345	$152.35	$152.35	$152.30
Purchase #3	$107.48	11.282%	$119.6059	$119.61	$119.60	$119.60
Purchase #4	$56.28	9.468%	$61.6086	$61.61	$61.60	$61.60
Purchase #5	$80.46	13.705%	$91.487	$91.49	$91.50	$91.50
Purchase #6	$229.54	10.507%	$253.6578	$253.66	$253.65	$253.70
Purchase #7	$129.93	9.696%	$142.528	$142.53	$142.55	$142.50
7 purchase totals =	$912.46		$1,000.9493	$1,000.97	$1,000.95	$1,000.90