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	$46.75	11.724%	$52.231	$52.23	$52.25	$52.20
Purchase #2	$179.42	4.635%	$187.7361	$187.74	$187.75	$187.70
Purchase #3	$93.89	5.541%	$99.0924	$99.09	$99.10	$99.10
Purchase #4	$146.32	7.470%	$157.2501	$157.25	$157.25	$157.30
Purchase #5	$192.89	12.392%	$216.7929	$216.79	$216.80	$216.80
Purchase #6	$112.55	5.805%	$119.0835	$119.08	$119.10	$119.10
Purchase #7	$164.98	12.287%	$185.2511	$185.25	$185.25	$185.30
7 purchase totals =	$936.80		$1,017.4371	$1,017.43	$1,017.50	$1,017.50