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	$173.42	13.584%	$196.9774	$196.98	$197.00	$197.00
Purchase #2	$57.38	11.257%	$63.8393	$63.84	$63.85	$63.80
Purchase #3	$96.34	5.281%	$101.4277	$101.43	$101.45	$101.40
Purchase #4	$94.62	11.834%	$105.8173	$105.82	$105.80	$105.80
Purchase #5	$88.84	12.424%	$99.8775	$99.88	$99.90	$99.90
Purchase #6	$244.45	13.643%	$277.8003	$277.80	$277.80	$277.80
Purchase #7	$111.54	11.470%	$124.3336	$124.33	$124.35	$124.30
7 purchase totals =	$866.59		$970.0731	$970.08	$970.15	$970.00