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	$112.96	9.283%	$123.4461	$123.45	$123.45	$123.40
Purchase #2	$200.44	11.501%	$223.4926	$223.49	$223.50	$223.50
Purchase #3	$47.58	4.242%	$49.5983	$49.60	$49.60	$49.60
Purchase #4	$189.67	4.549%	$198.2981	$198.30	$198.30	$198.30
Purchase #5	$39.93	4.560%	$41.7508	$41.75	$41.75	$41.80
Purchase #6	$87.30	6.386%	$92.875	$92.88	$92.90	$92.90
Purchase #7	$34.74	7.479%	$37.3382	$37.34	$37.35	$37.30
7 purchase totals =	$712.62		$766.7991	$766.81	$766.85	$766.80