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	$233.51	12.840%	$263.4927	$263.49	$263.50	$263.50
Purchase #2	$203.61	7.262%	$218.3962	$218.40	$218.40	$218.40
Purchase #3	$70.74	11.474%	$78.8567	$78.86	$78.85	$78.90
Purchase #4	$67.25	5.420%	$70.895	$70.90	$70.90	$70.90
Purchase #5	$204.28	12.471%	$229.7558	$229.76	$229.75	$229.80
Purchase #6	$113.55	7.738%	$122.3365	$122.34	$122.35	$122.30
Purchase #7	$80.57	3.667%	$83.5245	$83.52	$83.50	$83.50
7 purchase totals =	$973.51		$1,067.2574	$1,067.27	$1,067.25	$1,067.30