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	$158.43	5.492%	$167.131	$167.13	$167.15	$167.10
Purchase #2	$77.99	11.486%	$86.9479	$86.95	$86.95	$86.90
Purchase #3	$171.61	10.739%	$190.0392	$190.04	$190.05	$190.00
Purchase #4	$156.64	6.119%	$166.2248	$166.22	$166.20	$166.20
Purchase #5	$203.41	8.715%	$221.1372	$221.14	$221.15	$221.10
Purchase #6	$120.47	6.839%	$128.7089	$128.71	$128.70	$128.70
Purchase #7	$142.51	9.703%	$156.3377	$156.34	$156.35	$156.30
7 purchase totals =	$1,031.06		$1,116.5267	$1,116.53	$1,116.55	$1,116.30