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	$242.80	13.358%	$275.2332	$275.23	$275.25	$275.20
Purchase #2	$53.33	6.841%	$56.9783	$56.98	$57.00	$57.00
Purchase #3	$81.56	4.827%	$85.4969	$85.50	$85.50	$85.50
Purchase #4	$237.65	10.264%	$262.0424	$262.04	$262.05	$262.00
Purchase #5	$137.58	3.289%	$142.105	$142.11	$142.10	$142.10
Purchase #6	$211.34	4.799%	$221.4822	$221.48	$221.50	$221.50
Purchase #7	$83.47	5.283%	$87.8797	$87.88	$87.90	$87.90
7 purchase totals =	$1,047.73		$1,131.2177	$1,131.22	$1,131.30	$1,131.20