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	$87.37	13.259%	$98.9544	$98.95	$98.95	$99.00
Purchase #2	$240.55	12.206%	$269.9115	$269.91	$269.90	$269.90
Purchase #3	$64.68	3.865%	$67.1799	$67.18	$67.20	$67.20
Purchase #4	$88.52	6.532%	$94.3021	$94.30	$94.30	$94.30
Purchase #5	$150.52	10.836%	$166.8303	$166.83	$166.85	$166.80
Purchase #6	$92.83	11.593%	$103.5918	$103.59	$103.60	$103.60
Purchase #7	$70.41	4.812%	$73.7981	$73.80	$73.80	$73.80
7 purchase totals =	$794.88		$874.5681	$874.56	$874.60	$874.60