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	$201.83	10.760%	$223.5469	$223.55	$223.55	$223.50
Purchase #2	$39.45	7.451%	$42.3894	$42.39	$42.40	$42.40
Purchase #3	$6.40	7.133%	$6.8565	$6.86	$6.85	$6.90
Purchase #4	$159.58	7.250%	$171.1496	$171.15	$171.15	$171.10
Purchase #5	$216.69	6.502%	$230.7792	$230.78	$230.80	$230.80
Purchase #6	$80.96	12.546%	$91.1172	$91.12	$91.10	$91.10
Purchase #7	$249.78	11.850%	$279.3789	$279.38	$279.40	$279.40
7 purchase totals =	$954.69		$1,045.2177	$1,045.23	$1,045.25	$1,045.20