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	$71.41	7.853%	$77.0178	$77.02	$77.00	$77.00
Purchase #2	$125.89	9.404%	$137.7287	$137.73	$137.75	$137.70
Purchase #3	$100.64	8.443%	$109.137	$109.14	$109.15	$109.10
Purchase #4	$150.71	11.566%	$168.1411	$168.14	$168.15	$168.10
Purchase #5	$211.43	5.714%	$223.5111	$223.51	$223.50	$223.50
Purchase #6	$128.57	9.338%	$140.5759	$140.58	$140.60	$140.60
Purchase #7	$104.94	11.865%	$117.3911	$117.39	$117.40	$117.40
7 purchase totals =	$893.59		$973.5027	$973.51	$973.55	$973.40