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	$60.60	11.817%	$67.7611	$67.76	$67.75	$67.80
Purchase #2	$59.28	13.672%	$67.3848	$67.38	$67.40	$67.40
Purchase #3	$81.71	4.557%	$85.4335	$85.43	$85.45	$85.40
Purchase #4	$119.65	9.794%	$131.3685	$131.37	$131.35	$131.40
Purchase #5	$125.69	10.690%	$139.1263	$139.13	$139.15	$139.10
Purchase #6	$195.92	10.402%	$216.2996	$216.30	$216.30	$216.30
Purchase #7	$6.60	3.699%	$6.8441	$6.84	$6.85	$6.80
7 purchase totals =	$649.45		$714.2179	$714.21	$714.25	$714.20