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	$23.93	9.163%	$26.1227	$26.12	$26.10	$26.10
Purchase #2	$56.56	8.193%	$61.194	$61.19	$61.20	$61.20
Purchase #3	$55.31	4.642%	$57.8775	$57.88	$57.90	$57.90
Purchase #4	$70.70	4.475%	$73.8638	$73.86	$73.85	$73.90
Purchase #5	$53.97	10.800%	$59.7988	$59.80	$59.80	$59.80
Purchase #6	$191.44	3.650%	$198.4276	$198.43	$198.45	$198.40
Purchase #7	$50.38	10.117%	$55.4769	$55.48	$55.50	$55.50
7 purchase totals =	$502.29		$532.7613	$532.76	$532.80	$532.80