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	$157.95	4.300%	$164.7419	$164.74	$164.75	$164.70
Purchase #2	$100.78	4.761%	$105.5781	$105.58	$105.60	$105.60
Purchase #3	$201.38	10.760%	$223.0485	$223.05	$223.05	$223.00
Purchase #4	$160.50	13.165%	$181.6298	$181.63	$181.65	$181.60
Purchase #5	$247.64	12.788%	$279.3082	$279.31	$279.30	$279.30
Purchase #6	$129.49	10.786%	$143.4568	$143.46	$143.45	$143.50
Purchase #7	$129.53	13.655%	$147.2173	$147.22	$147.20	$147.20
7 purchase totals =	$1,127.27		$1,244.9806	$1,244.99	$1,245.00	$1,244.90