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	$209.42	11.446%	$233.3902	$233.39	$233.40	$233.40
Purchase #2	$96.65	3.315%	$99.8539	$99.85	$99.85	$99.90
Purchase #3	$99.37	12.322%	$111.6144	$111.61	$111.60	$111.60
Purchase #4	$79.94	13.749%	$90.931	$90.93	$90.95	$90.90
Purchase #5	$71.95	3.469%	$74.4459	$74.45	$74.45	$74.40
Purchase #6	$94.52	4.626%	$98.8925	$98.89	$98.90	$98.90
Purchase #7	$28.54	13.243%	$32.3196	$32.32	$32.30	$32.30
7 purchase totals =	$680.39		$741.4475	$741.44	$741.45	$741.40