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	$81.37	5.477%	$85.8266	$85.83	$85.85	$85.80
Purchase #2	$190.96	12.653%	$215.1222	$215.12	$215.10	$215.10
Purchase #3	$222.31	12.674%	$250.4856	$250.49	$250.50	$250.50
Purchase #4	$65.42	7.255%	$70.1662	$70.17	$70.15	$70.20
Purchase #5	$124.54	5.574%	$131.4819	$131.48	$131.50	$131.50
Purchase #6	$79.37	4.800%	$83.1798	$83.18	$83.20	$83.20
Purchase #7	$172.68	9.593%	$189.2452	$189.25	$189.25	$189.20
7 purchase totals =	$936.65		$1,025.5075	$1,025.52	$1,025.55	$1,025.50