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	$148.29	3.642%	$153.6907	$153.69	$153.70	$153.70
Purchase #2	$91.35	3.499%	$94.5463	$94.55	$94.55	$94.50
Purchase #3	$67.85	7.643%	$73.0358	$73.04	$73.05	$73.00
Purchase #4	$61.92	13.323%	$70.1696	$70.17	$70.15	$70.20
Purchase #5	$102.48	6.466%	$109.1064	$109.11	$109.10	$109.10
Purchase #6	$86.90	4.558%	$90.8609	$90.86	$90.85	$90.90
Purchase #7	$179.51	13.675%	$204.058	$204.06	$204.05	$204.10
7 purchase totals =	$738.30		$795.4677	$795.48	$795.45	$795.50