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	$130.52	9.275%	$142.6257	$142.63	$142.65	$142.60
Purchase #2	$38.49	4.762%	$40.3229	$40.32	$40.30	$40.30
Purchase #3	$125.89	7.724%	$135.6137	$135.61	$135.60	$135.60
Purchase #4	$211.31	10.486%	$233.468	$233.47	$233.45	$233.50
Purchase #5	$90.94	8.815%	$98.9564	$98.96	$98.95	$99.00
Purchase #6	$238.31	13.315%	$270.041	$270.04	$270.05	$270.00
Purchase #7	$136.35	11.669%	$152.2607	$152.26	$152.25	$152.30
7 purchase totals =	$971.81		$1,073.2884	$1,073.29	$1,073.25	$1,073.30