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	$53.58	12.742%	$60.4072	$60.41	$60.40	$60.40
Purchase #2	$145.88	3.177%	$150.5146	$150.51	$150.50	$150.50
Purchase #3	$153.58	4.729%	$160.8428	$160.84	$160.85	$160.80
Purchase #4	$138.28	9.634%	$151.6019	$151.60	$151.60	$151.60
Purchase #5	$176.26	3.765%	$182.8962	$182.90	$182.90	$182.90
Purchase #6	$142.52	8.591%	$154.7639	$154.76	$154.75	$154.80
Purchase #7	$200.36	11.559%	$223.5196	$223.52	$223.50	$223.50
7 purchase totals =	$1,010.46		$1,084.5462	$1,084.54	$1,084.50	$1,084.50