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	$113.95	8.480%	$123.613	$123.61	$123.60	$123.60
Purchase #2	$137.27	11.322%	$152.8117	$152.81	$152.80	$152.80
Purchase #3	$196.63	3.728%	$203.9604	$203.96	$203.95	$204.00
Purchase #4	$153.33	10.842%	$169.954	$169.95	$169.95	$170.00
Purchase #5	$45.68	3.714%	$47.3766	$47.38	$47.40	$47.40
Purchase #6	$243.72	10.727%	$269.8638	$269.86	$269.85	$269.90
Purchase #7	$169.54	11.243%	$188.6014	$188.60	$188.60	$188.60
7 purchase totals =	$1,060.12		$1,156.1809	$1,156.17	$1,156.15	$1,156.30