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	$7.97	4.451%	$8.3247	$8.32	$8.30	$8.30
Purchase #2	$87.53	4.322%	$91.313	$91.31	$91.30	$91.30
Purchase #3	$29.91	4.343%	$31.209	$31.21	$31.20	$31.20
Purchase #4	$64.38	4.434%	$67.2346	$67.23	$67.25	$67.20
Purchase #5	$29.67	11.798%	$33.1705	$33.17	$33.15	$33.20
Purchase #6	$91.55	8.578%	$99.4032	$99.40	$99.40	$99.40
Purchase #7	$132.88	6.622%	$141.6793	$141.68	$141.70	$141.70
7 purchase totals =	$443.89		$472.3343	$472.32	$472.30	$472.30