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	$44.71	7.790%	$48.1929	$48.19	$48.20	$48.20
Purchase #2	$134.98	11.692%	$150.7619	$150.76	$150.75	$150.80
Purchase #3	$80.84	3.799%	$83.9111	$83.91	$83.90	$83.90
Purchase #4	$81.60	7.506%	$87.7249	$87.72	$87.70	$87.70
Purchase #5	$230.83	5.476%	$243.4703	$243.47	$243.45	$243.50
Purchase #6	$185.34	3.537%	$191.8955	$191.90	$191.90	$191.90
Purchase #7	$61.64	12.726%	$69.4843	$69.48	$69.50	$69.50
7 purchase totals =	$819.94		$875.4409	$875.43	$875.40	$875.50