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	$108.72	13.285%	$123.1635	$123.16	$123.15	$123.20
Purchase #2	$242.52	11.104%	$269.4494	$269.45	$269.45	$269.40
Purchase #3	$128.61	10.622%	$142.271	$142.27	$142.25	$142.30
Purchase #4	$216.88	5.288%	$228.3486	$228.35	$228.35	$228.30
Purchase #5	$110.32	3.790%	$114.5011	$114.50	$114.50	$114.50
Purchase #6	$121.41	11.663%	$135.57	$135.57	$135.55	$135.60
Purchase #7	$183.48	12.510%	$206.4333	$206.43	$206.45	$206.40
7 purchase totals =	$1,111.94		$1,219.7369	$1,219.73	$1,219.70	$1,219.70