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	$87.73	7.690%	$94.4764	$94.48	$94.50	$94.50
Purchase #2	$11.30	8.166%	$12.2228	$12.22	$12.20	$12.20
Purchase #3	$42.91	8.557%	$46.5818	$46.58	$46.60	$46.60
Purchase #4	$27.59	3.736%	$28.6208	$28.62	$28.60	$28.60
Purchase #5	$208.92	9.363%	$228.4812	$228.48	$228.50	$228.50
Purchase #6	$44.29	3.495%	$45.8379	$45.84	$45.85	$45.80
Purchase #7	$70.44	3.115%	$72.6342	$72.63	$72.65	$72.60
7 purchase totals =	$493.18		$528.8551	$528.85	$528.90	$528.80