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	$172.80	13.452%	$196.0451	$196.05	$196.05	$196.00
Purchase #2	$177.47	6.742%	$189.435	$189.44	$189.45	$189.40
Purchase #3	$203.42	6.476%	$216.5935	$216.59	$216.60	$216.60
Purchase #4	$123.40	11.272%	$137.3096	$137.31	$137.30	$137.30
Purchase #5	$50.35	10.468%	$55.6206	$55.62	$55.60	$55.60
Purchase #6	$210.98	11.399%	$235.0296	$235.03	$235.05	$235.00
Purchase #7	$244.32	9.817%	$268.3049	$268.30	$268.30	$268.30
7 purchase totals =	$1,182.74		$1,298.3383	$1,298.34	$1,298.35	$1,298.20