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	10.631%	$175.2727	$175.27	$175.25	$175.30
Purchase #2	$74.53	3.769%	$77.339	$77.34	$77.35	$77.30
Purchase #3	$243.92	8.258%	$264.0629	$264.06	$264.05	$264.10
Purchase #4	$94.62	7.787%	$101.9881	$101.99	$102.00	$102.00
Purchase #5	$100.58	13.801%	$114.461	$114.46	$114.45	$114.50
Purchase #6	$154.49	9.105%	$168.5563	$168.56	$168.55	$168.60
Purchase #7	$63.75	12.184%	$71.5173	$71.52	$71.50	$71.50
7 purchase totals =	$890.32		$973.1973	$973.20	$973.15	$973.30