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	$161.71	12.206%	$181.4483	$181.45	$181.45	$181.40
Purchase #2	$33.44	10.281%	$36.878	$36.88	$36.90	$36.90
Purchase #3	$47.25	9.813%	$51.8866	$51.89	$51.90	$51.90
Purchase #4	$45.75	3.196%	$47.2122	$47.21	$47.20	$47.20
Purchase #5	$50.36	10.435%	$55.6151	$55.62	$55.60	$55.60
Purchase #6	$81.41	10.356%	$89.8408	$89.84	$89.85	$89.80
Purchase #7	$105.40	4.810%	$110.4697	$110.47	$110.45	$110.50
7 purchase totals =	$525.32		$573.3507	$573.36	$573.35	$573.30