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	$64.56	4.136%	$67.2302	$67.23	$67.25	$67.20
Purchase #2	$34.34	9.125%	$37.4735	$37.47	$37.45	$37.50
Purchase #3	$248.28	11.736%	$277.4181	$277.42	$277.40	$277.40
Purchase #4	$100.38	13.719%	$114.1511	$114.15	$114.15	$114.20
Purchase #5	$232.76	13.280%	$263.6705	$263.67	$263.65	$263.70
Purchase #6	$100.60	13.605%	$114.2866	$114.29	$114.30	$114.30
Purchase #7	$211.34	5.739%	$223.4688	$223.47	$223.45	$223.50
7 purchase totals =	$992.26		$1,097.6988	$1,097.70	$1,097.65	$1,097.80