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	$178.37	5.185%	$187.6185	$187.62	$187.60	$187.60
Purchase #2	$225.69	9.499%	$247.1283	$247.13	$247.15	$247.10
Purchase #3	$172.46	7.415%	$185.2479	$185.25	$185.25	$185.20
Purchase #4	$35.57	5.743%	$37.6128	$37.61	$37.60	$37.60
Purchase #5	$12.69	6.444%	$13.5077	$13.51	$13.50	$13.50
Purchase #6	$245.29	13.125%	$277.4843	$277.48	$277.50	$277.50
Purchase #7	$140.41	11.686%	$156.8183	$156.82	$156.80	$156.80
7 purchase totals =	$1,010.48		$1,105.4178	$1,105.42	$1,105.40	$1,105.30