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	$247.42	6.187%	$262.7279	$262.73	$262.75	$262.70
Purchase #2	$42.63	4.787%	$44.6707	$44.67	$44.65	$44.70
Purchase #3	$216.36	6.480%	$230.3801	$230.38	$230.40	$230.40
Purchase #4	$79.30	12.601%	$89.2926	$89.29	$89.30	$89.30
Purchase #5	$30.32	5.257%	$31.9139	$31.91	$31.90	$31.90
Purchase #6	$18.97	6.319%	$20.1687	$20.17	$20.15	$20.20
Purchase #7	$178.27	3.869%	$185.1673	$185.17	$185.15	$185.20
7 purchase totals =	$813.27		$864.3212	$864.32	$864.30	$864.40