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	$212.41	4.650%	$222.2871	$222.29	$222.30	$222.30
Purchase #2	$148.91	5.670%	$157.3532	$157.35	$157.35	$157.40
Purchase #3	$180.49	12.598%	$203.2281	$203.23	$203.25	$203.20
Purchase #4	$236.90	12.736%	$267.0716	$267.07	$267.05	$267.10
Purchase #5	$79.92	12.134%	$89.6175	$89.62	$89.60	$89.60
Purchase #6	$29.36	11.760%	$32.8127	$32.81	$32.80	$32.80
Purchase #7	$79.71	3.202%	$82.2623	$82.26	$82.25	$82.30
7 purchase totals =	$967.70		$1,054.6325	$1,054.63	$1,054.60	$1,054.70