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	$95.89	6.727%	$102.3405	$102.34	$102.35	$102.30
Purchase #2	$179.77	6.740%	$191.8865	$191.89	$191.90	$191.90
Purchase #3	$104.30	11.336%	$116.1234	$116.12	$116.10	$116.10
Purchase #4	$47.93	13.792%	$54.5405	$54.54	$54.55	$54.50
Purchase #5	$202.43	4.415%	$211.3673	$211.37	$211.35	$211.40
Purchase #6	$11.30	6.747%	$12.0624	$12.06	$12.05	$12.10
Purchase #7	$247.72	3.462%	$256.2961	$256.30	$256.30	$256.30
7 purchase totals =	$889.34		$944.6167	$944.62	$944.60	$944.60