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	$36.44	9.240%	$39.8071	$39.81	$39.80	$39.80
Purchase #2	$56.49	9.537%	$61.8775	$61.88	$61.90	$61.90
Purchase #3	$33.46	11.568%	$37.3307	$37.33	$37.35	$37.30
Purchase #4	$42.44	5.681%	$44.851	$44.85	$44.85	$44.90
Purchase #5	$180.92	8.669%	$196.604	$196.60	$196.60	$196.60
Purchase #6	$236.63	3.317%	$244.479	$244.48	$244.50	$244.50
Purchase #7	$22.68	11.551%	$25.2998	$25.30	$25.30	$25.30
7 purchase totals =	$609.06		$650.2491	$650.25	$650.30	$650.30