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	$173.82	13.385%	$197.0858	$197.09	$197.10	$197.10
Purchase #2	$52.74	13.250%	$59.7281	$59.73	$59.75	$59.70
Purchase #3	$175.57	5.318%	$184.9068	$184.91	$184.90	$184.90
Purchase #4	$205.58	13.560%	$233.4566	$233.46	$233.45	$233.50
Purchase #5	$25.59	8.853%	$27.8555	$27.86	$27.85	$27.90
Purchase #6	$173.37	8.607%	$188.292	$188.29	$188.30	$188.30
Purchase #7	$73.37	9.340%	$80.2228	$80.22	$80.20	$80.20
7 purchase totals =	$880.04		$971.5476	$971.56	$971.55	$971.60