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	$173.85	4.679%	$181.9844	$181.98	$182.00	$182.00
Purchase #2	$28.56	13.813%	$32.505	$32.51	$32.50	$32.50
Purchase #3	$187.29	8.554%	$203.3108	$203.31	$203.30	$203.30
Purchase #4	$92.86	8.179%	$100.455	$100.46	$100.45	$100.50
Purchase #5	$168.30	13.507%	$191.0323	$191.03	$191.05	$191.00
Purchase #6	$85.96	6.675%	$91.6978	$91.70	$91.70	$91.70
Purchase #7	$222.61	6.476%	$237.0262	$237.03	$237.05	$237.00
7 purchase totals =	$959.43		$1,038.0115	$1,038.02	$1,038.05	$1,038.00