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	$39.77	10.233%	$43.8397	$43.84	$43.85	$43.80
Purchase #2	$79.27	13.865%	$90.2608	$90.26	$90.25	$90.30
Purchase #3	$180.31	5.116%	$189.5347	$189.53	$189.55	$189.50
Purchase #4	$184.86	5.525%	$195.0735	$195.07	$195.05	$195.10
Purchase #5	$124.66	13.368%	$141.3245	$141.32	$141.30	$141.30
Purchase #6	$23.39	4.167%	$24.3647	$24.36	$24.35	$24.40
Purchase #7	$55.41	7.107%	$59.348	$59.35	$59.35	$59.30
7 purchase totals =	$687.67		$743.7459	$743.73	$743.70	$743.70