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	$57.30	7.858%	$61.8026	$61.80	$61.80	$61.80
Purchase #2	$76.80	5.351%	$80.9096	$80.91	$80.90	$80.90
Purchase #3	$148.28	5.764%	$156.8269	$156.83	$156.85	$156.80
Purchase #4	$99.43	10.351%	$109.722	$109.72	$109.70	$109.70
Purchase #5	$91.46	4.317%	$95.4083	$95.41	$95.40	$95.40
Purchase #6	$94.64	13.621%	$107.5309	$107.53	$107.55	$107.50
Purchase #7	$110.41	12.682%	$124.4122	$124.41	$124.40	$124.40
7 purchase totals =	$678.32		$736.6125	$736.61	$736.60	$736.50