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	$41.88	11.641%	$46.7553	$46.76	$46.75	$46.80
Purchase #2	$224.75	12.775%	$253.4618	$253.46	$253.45	$253.50
Purchase #3	$57.72	11.137%	$64.1483	$64.15	$64.15	$64.10
Purchase #4	$131.43	12.808%	$148.2636	$148.26	$148.25	$148.30
Purchase #5	$250.59	8.630%	$272.2159	$272.22	$272.20	$272.20
Purchase #6	$69.52	4.604%	$72.7207	$72.72	$72.70	$72.70
Purchase #7	$178.33	12.417%	$200.4732	$200.47	$200.45	$200.50
7 purchase totals =	$954.22		$1,058.0388	$1,058.04	$1,057.95	$1,058.10