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	$247.31	11.420%	$275.5528	$275.55	$275.55	$275.60
Purchase #2	$249.90	10.531%	$276.217	$276.22	$276.20	$276.20
Purchase #3	$30.53	4.122%	$31.7884	$31.79	$31.80	$31.80
Purchase #4	$149.67	10.478%	$165.3524	$165.35	$165.35	$165.40
Purchase #5	$9.79	6.144%	$10.3915	$10.39	$10.40	$10.40
Purchase #6	$52.85	12.749%	$59.5878	$59.59	$59.60	$59.60
Purchase #7	$247.73	10.264%	$273.157	$273.16	$273.15	$273.20
7 purchase totals =	$987.78		$1,092.0469	$1,092.05	$1,092.05	$1,092.20