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	$152.46	4.776%	$159.7415	$159.74	$159.75	$159.70
Purchase #2	$99.78	9.265%	$109.0246	$109.02	$109.00	$109.00
Purchase #3	$85.95	4.200%	$89.5599	$89.56	$89.55	$89.60
Purchase #4	$115.80	10.362%	$127.7992	$127.80	$127.80	$127.80
Purchase #5	$216.40	11.688%	$241.6928	$241.69	$241.70	$241.70
Purchase #6	$83.79	13.714%	$95.281	$95.28	$95.30	$95.30
Purchase #7	$44.86	9.702%	$49.2123	$49.21	$49.20	$49.20
7 purchase totals =	$799.04		$872.3113	$872.30	$872.30	$872.30