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	$231.73	6.285%	$246.2942	$246.29	$246.30	$246.30
Purchase #2	$28.78	13.557%	$32.6817	$32.68	$32.70	$32.70
Purchase #3	$182.75	7.309%	$196.1072	$196.11	$196.10	$196.10
Purchase #4	$57.40	7.716%	$61.829	$61.83	$61.85	$61.80
Purchase #5	$20.44	7.146%	$21.9006	$21.90	$21.90	$21.90
Purchase #6	$56.97	13.599%	$64.7174	$64.72	$64.70	$64.70
Purchase #7	$133.84	5.369%	$141.0259	$141.03	$141.05	$141.00
7 purchase totals =	$711.91		$764.5560	$764.56	$764.60	$764.50