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	$101.56	12.448%	$114.2022	$114.20	$114.20	$114.20
Purchase #2	$86.58	5.647%	$91.4692	$91.47	$91.45	$91.50
Purchase #3	$140.82	3.438%	$145.6614	$145.66	$145.65	$145.70
Purchase #4	$97.64	7.430%	$104.8947	$104.89	$104.90	$104.90
Purchase #5	$38.76	12.785%	$43.7155	$43.72	$43.70	$43.70
Purchase #6	$167.69	13.585%	$190.4707	$190.47	$190.45	$190.50
Purchase #7	$145.86	5.814%	$154.3403	$154.34	$154.35	$154.30
7 purchase totals =	$778.91		$844.7540	$844.75	$844.70	$844.80