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	$92.94	13.424%	$105.4163	$105.42	$105.40	$105.40
Purchase #2	$232.73	9.550%	$254.9557	$254.96	$254.95	$255.00
Purchase #3	$90.80	11.705%	$101.4281	$101.43	$101.45	$101.40
Purchase #4	$66.41	6.390%	$70.6536	$70.65	$70.65	$70.70
Purchase #5	$31.85	4.515%	$33.288	$33.29	$33.30	$33.30
Purchase #6	$205.70	6.420%	$218.9059	$218.91	$218.90	$218.90
Purchase #7	$202.55	10.531%	$223.8805	$223.88	$223.90	$223.90
7 purchase totals =	$922.98		$1,008.5281	$1,008.54	$1,008.55	$1,008.60