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	$141.57	7.617%	$152.3534	$152.35	$152.35	$152.40
Purchase #2	$88.87	13.572%	$100.9314	$100.93	$100.95	$100.90
Purchase #3	$208.28	7.485%	$223.8698	$223.87	$223.85	$223.90
Purchase #4	$30.54	12.414%	$34.3312	$34.33	$34.35	$34.30
Purchase #5	$84.32	8.304%	$91.3219	$91.32	$91.30	$91.30
Purchase #6	$41.77	6.655%	$44.5498	$44.55	$44.55	$44.50
Purchase #7	$67.96	8.217%	$73.5443	$73.54	$73.55	$73.50
7 purchase totals =	$663.31		$720.9018	$720.89	$720.90	$720.80