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	$232.89	4.667%	$243.759	$243.76	$243.75	$243.80
Purchase #2	$33.91	12.726%	$38.2254	$38.23	$38.25	$38.20
Purchase #3	$87.38	8.309%	$94.6404	$94.64	$94.65	$94.60
Purchase #4	$139.93	4.736%	$146.5571	$146.56	$146.55	$146.60
Purchase #5	$204.45	8.325%	$221.4705	$221.47	$221.45	$221.50
Purchase #6	$144.94	5.756%	$153.2827	$153.28	$153.30	$153.30
Purchase #7	$122.38	11.850%	$136.882	$136.88	$136.90	$136.90
7 purchase totals =	$965.88		$1,034.8171	$1,034.82	$1,034.85	$1,034.90