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	$139.78	3.790%	$145.0777	$145.08	$145.10	$145.10
Purchase #2	$52.28	13.548%	$59.3629	$59.36	$59.35	$59.40
Purchase #3	$100.85	3.492%	$104.3717	$104.37	$104.35	$104.40
Purchase #4	$223.37	9.558%	$244.7197	$244.72	$244.70	$244.70
Purchase #5	$60.88	6.327%	$64.7319	$64.73	$64.75	$64.70
Purchase #6	$30.25	3.856%	$31.4164	$31.42	$31.40	$31.40
Purchase #7	$138.65	12.825%	$156.4319	$156.43	$156.45	$156.40
7 purchase totals =	$746.06		$806.1122	$806.11	$806.10	$806.10