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	$221.36	8.614%	$240.428	$240.43	$240.45	$240.40
Purchase #2	$240.38	7.455%	$258.3003	$258.30	$258.30	$258.30
Purchase #3	$110.56	7.551%	$118.9084	$118.91	$118.90	$118.90
Purchase #4	$99.41	13.824%	$113.1524	$113.15	$113.15	$113.20
Purchase #5	$185.65	10.679%	$205.4756	$205.48	$205.50	$205.50
Purchase #6	$171.86	13.233%	$194.6022	$194.60	$194.60	$194.60
Purchase #7	$72.96	7.821%	$78.6662	$78.67	$78.65	$78.70
7 purchase totals =	$1,102.18		$1,209.5331	$1,209.54	$1,209.55	$1,209.60