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	$245.95	3.827%	$255.3625	$255.36	$255.35	$255.40
Purchase #2	$190.53	4.506%	$199.1153	$199.12	$199.10	$199.10
Purchase #3	$98.65	9.271%	$107.7958	$107.80	$107.80	$107.80
Purchase #4	$57.46	3.164%	$59.278	$59.28	$59.30	$59.30
Purchase #5	$74.62	10.801%	$82.6797	$82.68	$82.70	$82.70
Purchase #6	$175.67	9.803%	$192.8909	$192.89	$192.90	$192.90
Purchase #7	$134.56	4.580%	$140.7228	$140.72	$140.70	$140.70
7 purchase totals =	$977.44		$1,037.8450	$1,037.85	$1,037.85	$1,037.90