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	$58.32	6.154%	$61.909	$61.91	$61.90	$61.90
Purchase #2	$140.83	3.546%	$145.8238	$145.82	$145.80	$145.80
Purchase #3	$214.98	7.543%	$231.1959	$231.20	$231.20	$231.20
Purchase #4	$157.37	9.196%	$171.8417	$171.84	$171.85	$171.80
Purchase #5	$145.41	13.761%	$165.4199	$165.42	$165.40	$165.40
Purchase #6	$85.48	7.503%	$91.8936	$91.89	$91.90	$91.90
Purchase #7	$148.56	5.675%	$156.9908	$156.99	$157.00	$157.00
7 purchase totals =	$950.95		$1,025.0747	$1,025.07	$1,025.05	$1,025.00