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	$41.64	4.384%	$43.4655	$43.47	$43.45	$43.50
Purchase #2	$100.31	6.202%	$106.5312	$106.53	$106.55	$106.50
Purchase #3	$86.30	6.346%	$91.7766	$91.78	$91.80	$91.80
Purchase #4	$148.61	11.524%	$165.7358	$165.74	$165.75	$165.70
Purchase #5	$40.72	3.324%	$42.0735	$42.07	$42.05	$42.10
Purchase #6	$159.72	5.107%	$167.8769	$167.88	$167.90	$167.90
Purchase #7	$69.34	11.504%	$77.3169	$77.32	$77.30	$77.30
7 purchase totals =	$646.64		$694.7764	$694.79	$694.80	$694.80