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	$152.36	3.498%	$157.6896	$157.69	$157.70	$157.70
Purchase #2	$79.81	13.842%	$90.8573	$90.86	$90.85	$90.90
Purchase #3	$98.41	10.202%	$108.4498	$108.45	$108.45	$108.40
Purchase #4	$16.46	9.134%	$17.9635	$17.96	$17.95	$18.00
Purchase #5	$167.35	4.654%	$175.1385	$175.14	$175.15	$175.10
Purchase #6	$80.83	3.486%	$83.6477	$83.65	$83.65	$83.60
Purchase #7	$143.31	13.686%	$162.9234	$162.92	$162.90	$162.90
7 purchase totals =	$738.53		$796.6698	$796.67	$796.65	$796.60