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	$190.48	3.594%	$197.3259	$197.33	$197.35	$197.30
Purchase #2	$178.74	10.109%	$196.8088	$196.81	$196.80	$196.80
Purchase #3	$139.41	9.747%	$152.9983	$153.00	$153.00	$153.00
Purchase #4	$54.84	10.465%	$60.579	$60.58	$60.60	$60.60
Purchase #5	$172.56	7.633%	$185.7315	$185.73	$185.75	$185.70
Purchase #6	$141.83	6.145%	$150.5455	$150.55	$150.55	$150.50
Purchase #7	$39.65	8.213%	$42.9065	$42.91	$42.90	$42.90
7 purchase totals =	$917.51		$986.8955	$986.91	$986.95	$986.80