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	$104.67	8.426%	$113.4895	$113.49	$113.50	$113.50
Purchase #2	$23.80	6.488%	$25.3441	$25.34	$25.35	$25.30
Purchase #3	$56.50	5.723%	$59.7335	$59.73	$59.75	$59.70
Purchase #4	$176.86	6.832%	$188.9431	$188.94	$188.95	$188.90
Purchase #5	$40.63	11.441%	$45.2785	$45.28	$45.30	$45.30
Purchase #6	$129.96	7.197%	$139.3132	$139.31	$139.30	$139.30
Purchase #7	$103.43	7.694%	$111.3879	$111.39	$111.40	$111.40
7 purchase totals =	$635.85		$683.4898	$683.48	$683.55	$683.40