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	$150.75	4.402%	$157.386	$157.39	$157.40	$157.40
Purchase #2	$199.51	11.494%	$222.4417	$222.44	$222.45	$222.40
Purchase #3	$215.79	3.231%	$222.7622	$222.76	$222.75	$222.80
Purchase #4	$28.94	9.600%	$31.7182	$31.72	$31.70	$31.70
Purchase #5	$45.83	9.658%	$50.2563	$50.26	$50.25	$50.30
Purchase #6	$158.33	10.319%	$174.6681	$174.67	$174.65	$174.70
Purchase #7	$179.27	13.266%	$203.052	$203.05	$203.05	$203.10
7 purchase totals =	$978.42		$1,062.2845	$1,062.29	$1,062.25	$1,062.40