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	$91.84	8.443%	$99.5941	$99.59	$99.60	$99.60
Purchase #2	$209.56	11.213%	$233.058	$233.06	$233.05	$233.10
Purchase #3	$216.56	11.217%	$240.8515	$240.85	$240.85	$240.90
Purchase #4	$95.96	7.358%	$103.0207	$103.02	$103.00	$103.00
Purchase #5	$226.42	8.686%	$246.0868	$246.09	$246.10	$246.10
Purchase #6	$223.59	9.263%	$244.3011	$244.30	$244.30	$244.30
Purchase #7	$98.88	13.766%	$112.4918	$112.49	$112.50	$112.50
7 purchase totals =	$1,162.81		$1,279.4040	$1,279.40	$1,279.40	$1,279.50