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	$162.68	8.367%	$176.2914	$176.29	$176.30	$176.30
Purchase #2	$172.86	10.372%	$190.789	$190.79	$190.80	$190.80
Purchase #3	$133.88	6.272%	$142.277	$142.28	$142.30	$142.30
Purchase #4	$56.87	6.348%	$60.4801	$60.48	$60.50	$60.50
Purchase #5	$61.36	10.468%	$67.7832	$67.78	$67.80	$67.80
Purchase #6	$49.65	8.490%	$53.8653	$53.87	$53.85	$53.90
Purchase #7	$57.46	8.594%	$62.3981	$62.40	$62.40	$62.40
7 purchase totals =	$694.76		$753.8841	$753.89	$753.95	$754.00