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	$113.48	8.428%	$123.0441	$123.04	$123.05	$123.00
Purchase #2	$8.35	9.297%	$9.1263	$9.13	$9.15	$9.10
Purchase #3	$156.69	11.836%	$175.2358	$175.24	$175.25	$175.20
Purchase #4	$178.85	5.156%	$188.0715	$188.07	$188.05	$188.10
Purchase #5	$37.40	13.569%	$42.4748	$42.47	$42.45	$42.50
Purchase #6	$240.86	13.868%	$274.2625	$274.26	$274.25	$274.30
Purchase #7	$59.43	4.156%	$61.8999	$61.90	$61.90	$61.90
7 purchase totals =	$795.06		$874.1149	$874.11	$874.10	$874.10