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	$127.56	10.833%	$141.3786	$141.38	$141.40	$141.40
Purchase #2	$99.84	11.377%	$111.1988	$111.20	$111.20	$111.20
Purchase #3	$15.84	12.275%	$17.7844	$17.78	$17.80	$17.80
Purchase #4	$94.69	12.137%	$106.1825	$106.18	$106.20	$106.20
Purchase #5	$64.54	12.242%	$72.441	$72.44	$72.45	$72.40
Purchase #6	$42.45	7.765%	$45.7462	$45.75	$45.75	$45.70
Purchase #7	$61.56	9.800%	$67.5929	$67.59	$67.60	$67.60
7 purchase totals =	$506.48		$562.3244	$562.32	$562.40	$562.30