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	$131.61	8.280%	$142.5073	$142.51	$142.50	$142.50
Purchase #2	$230.31	7.301%	$247.1249	$247.12	$247.10	$247.10
Purchase #3	$46.37	10.865%	$51.4081	$51.41	$51.40	$51.40
Purchase #4	$160.72	10.250%	$177.1938	$177.19	$177.20	$177.20
Purchase #5	$242.98	13.476%	$275.724	$275.72	$275.70	$275.70
Purchase #6	$31.38	13.211%	$35.5256	$35.53	$35.55	$35.50
Purchase #7	$235.78	6.487%	$251.075	$251.08	$251.10	$251.10
7 purchase totals =	$1,079.15		$1,180.5587	$1,180.56	$1,180.55	$1,180.50