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	$227.72	11.608%	$254.1537	$254.15	$254.15	$254.20
Purchase #2	$211.33	5.429%	$222.8031	$222.80	$222.80	$222.80
Purchase #3	$141.88	7.345%	$152.3011	$152.30	$152.30	$152.30
Purchase #4	$64.88	13.830%	$73.8529	$73.85	$73.85	$73.90
Purchase #5	$139.73	7.833%	$150.6751	$150.68	$150.70	$150.70
Purchase #6	$113.45	5.632%	$119.8395	$119.84	$119.85	$119.80
Purchase #7	$176.86	3.862%	$183.6903	$183.69	$183.70	$183.70
7 purchase totals =	$1,075.85		$1,157.3157	$1,157.31	$1,157.35	$1,157.40