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	$157.30	4.511%	$164.3958	$164.40	$164.40	$164.40
Purchase #2	$130.33	5.204%	$137.1124	$137.11	$137.10	$137.10
Purchase #3	$79.84	6.612%	$85.119	$85.12	$85.10	$85.10
Purchase #4	$51.84	4.450%	$54.1469	$54.15	$54.15	$54.10
Purchase #5	$235.50	7.688%	$253.6052	$253.61	$253.60	$253.60
Purchase #6	$221.52	4.794%	$232.1397	$232.14	$232.15	$232.10
Purchase #7	$80.48	13.217%	$91.117	$91.12	$91.10	$91.10
7 purchase totals =	$956.81		$1,017.6360	$1,017.65	$1,017.60	$1,017.50