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	$157.31	8.729%	$171.0416	$171.04	$171.05	$171.00
Purchase #2	$26.70	7.822%	$28.7885	$28.79	$28.80	$28.80
Purchase #3	$191.70	4.645%	$200.6045	$200.60	$200.60	$200.60
Purchase #4	$161.90	6.859%	$173.0047	$173.00	$173.00	$173.00
Purchase #5	$55.31	6.731%	$59.0329	$59.03	$59.05	$59.00
Purchase #6	$100.66	4.802%	$105.4937	$105.49	$105.50	$105.50
Purchase #7	$242.28	9.486%	$265.2627	$265.26	$265.25	$265.30
7 purchase totals =	$935.86		$1,003.2286	$1,003.21	$1,003.25	$1,003.20