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	$39.45	10.780%	$43.7027	$43.70	$43.70	$43.70
Purchase #2	$179.55	3.523%	$185.8755	$185.88	$185.90	$185.90
Purchase #3	$152.34	8.791%	$165.7322	$165.73	$165.75	$165.70
Purchase #4	$31.59	13.427%	$35.8316	$35.83	$35.85	$35.80
Purchase #5	$222.35	13.504%	$252.3761	$252.38	$252.40	$252.40
Purchase #6	$167.78	12.173%	$188.2039	$188.20	$188.20	$188.20
Purchase #7	$148.41	4.113%	$154.5141	$154.51	$154.50	$154.50
7 purchase totals =	$941.47		$1,026.2361	$1,026.23	$1,026.30	$1,026.20