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	$35.26	5.431%	$37.175	$37.18	$37.20	$37.20
Purchase #2	$183.34	3.874%	$190.4426	$190.44	$190.45	$190.40
Purchase #3	$172.41	10.750%	$190.9441	$190.94	$190.95	$190.90
Purchase #4	$151.98	13.276%	$172.1569	$172.16	$172.15	$172.20
Purchase #5	$167.32	10.207%	$184.3984	$184.40	$184.40	$184.40
Purchase #6	$54.74	9.860%	$60.1374	$60.14	$60.15	$60.10
Purchase #7	$167.73	10.688%	$185.657	$185.66	$185.65	$185.70
7 purchase totals =	$932.78		$1,020.9114	$1,020.92	$1,020.95	$1,020.90