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	$134.69	13.120%	$152.3613	$152.36	$152.35	$152.40
Purchase #2	$9.86	10.277%	$10.8733	$10.87	$10.85	$10.90
Purchase #3	$97.37	13.187%	$110.2102	$110.21	$110.20	$110.20
Purchase #4	$149.72	6.722%	$159.7842	$159.78	$159.80	$159.80
Purchase #5	$52.28	5.641%	$55.2291	$55.23	$55.25	$55.20
Purchase #6	$92.34	7.287%	$99.0688	$99.07	$99.05	$99.10
Purchase #7	$41.46	10.666%	$45.8821	$45.88	$45.90	$45.90
7 purchase totals =	$577.72		$633.4090	$633.40	$633.40	$633.50