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	$221.39	9.671%	$242.8006	$242.80	$242.80	$242.80
Purchase #2	$40.83	3.498%	$42.2582	$42.26	$42.25	$42.30
Purchase #3	$71.28	4.374%	$74.3978	$74.40	$74.40	$74.40
Purchase #4	$206.31	7.795%	$222.3919	$222.39	$222.40	$222.40
Purchase #5	$26.55	5.669%	$28.0551	$28.06	$28.05	$28.10
Purchase #6	$243.91	6.348%	$259.3934	$259.39	$259.40	$259.40
Purchase #7	$85.92	5.645%	$90.7702	$90.77	$90.75	$90.80
7 purchase totals =	$896.19		$960.0672	$960.07	$960.05	$960.20