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	$146.98	3.330%	$151.8744	$151.87	$151.85	$151.90
Purchase #2	$22.68	9.512%	$24.8373	$24.84	$24.85	$24.80
Purchase #3	$84.83	12.156%	$95.1419	$95.14	$95.15	$95.10
Purchase #4	$133.96	9.716%	$146.9756	$146.98	$147.00	$147.00
Purchase #5	$196.32	4.630%	$205.4096	$205.41	$205.40	$205.40
Purchase #6	$238.59	6.853%	$254.9406	$254.94	$254.95	$254.90
Purchase #7	$172.61	5.471%	$182.0535	$182.05	$182.05	$182.10
7 purchase totals =	$995.97		$1,061.2329	$1,061.23	$1,061.25	$1,061.20