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	$191.48	4.774%	$200.6213	$200.62	$200.60	$200.60
Purchase #2	$151.31	10.264%	$166.8405	$166.84	$166.85	$166.80
Purchase #3	$22.97	9.761%	$25.2121	$25.21	$25.20	$25.20
Purchase #4	$122.86	3.705%	$127.412	$127.41	$127.40	$127.40
Purchase #5	$98.47	11.351%	$109.6473	$109.65	$109.65	$109.60
Purchase #6	$226.26	7.848%	$244.0169	$244.02	$244.00	$244.00
Purchase #7	$112.31	9.577%	$123.0659	$123.07	$123.05	$123.10
7 purchase totals =	$925.66		$996.8160	$996.82	$996.75	$996.70