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	$30.99	7.510%	$33.3173	$33.32	$33.30	$33.30
Purchase #2	$151.73	8.864%	$165.1793	$165.18	$165.20	$165.20
Purchase #3	$78.45	5.623%	$82.8612	$82.86	$82.85	$82.90
Purchase #4	$160.28	8.304%	$173.5897	$173.59	$173.60	$173.60
Purchase #5	$76.88	11.815%	$85.9634	$85.96	$85.95	$86.00
Purchase #6	$139.86	13.203%	$158.3257	$158.33	$158.35	$158.30
Purchase #7	$139.35	11.452%	$155.3084	$155.31	$155.30	$155.30
7 purchase totals =	$777.54		$854.5450	$854.55	$854.55	$854.60