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	$34.64	6.859%	$37.016	$37.02	$37.00	$37.00
Purchase #2	$63.32	6.614%	$67.508	$67.51	$67.50	$67.50
Purchase #3	$13.40	12.260%	$15.0428	$15.04	$15.05	$15.00
Purchase #4	$152.73	10.816%	$169.2493	$169.25	$169.25	$169.20
Purchase #5	$47.43	7.289%	$50.8872	$50.89	$50.90	$50.90
Purchase #6	$171.96	7.848%	$185.4554	$185.46	$185.45	$185.50
Purchase #7	$27.32	10.209%	$30.1091	$30.11	$30.10	$30.10
7 purchase totals =	$510.80		$555.2678	$555.28	$555.25	$555.20