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	$54.67	9.481%	$59.8533	$59.85	$59.85	$59.90
Purchase #2	$25.45	12.618%	$28.6613	$28.66	$28.65	$28.70
Purchase #3	$167.79	11.766%	$187.5322	$187.53	$187.55	$187.50
Purchase #4	$130.82	13.285%	$148.1994	$148.20	$148.20	$148.20
Purchase #5	$151.32	13.768%	$172.1537	$172.15	$172.15	$172.20
Purchase #6	$47.45	10.155%	$52.2685	$52.27	$52.25	$52.30
Purchase #7	$192.39	6.849%	$205.5668	$205.57	$205.55	$205.60
7 purchase totals =	$769.89		$854.2352	$854.23	$854.20	$854.40