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	$43.61	10.758%	$48.3016	$48.30	$48.30	$48.30
Purchase #2	$169.66	3.807%	$176.119	$176.12	$176.10	$176.10
Purchase #3	$149.74	13.523%	$169.9893	$169.99	$170.00	$170.00
Purchase #4	$120.83	7.799%	$130.2535	$130.25	$130.25	$130.30
Purchase #5	$44.26	3.820%	$45.9507	$45.95	$45.95	$46.00
Purchase #6	$83.71	13.512%	$95.0209	$95.02	$95.00	$95.00
Purchase #7	$78.72	13.807%	$89.5889	$89.59	$89.60	$89.60
7 purchase totals =	$690.53		$755.2239	$755.22	$755.20	$755.30