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	$188.63	4.270%	$196.6845	$196.68	$196.70	$196.70
Purchase #2	$57.29	11.284%	$63.7546	$63.75	$63.75	$63.80
Purchase #3	$120.84	13.179%	$136.7655	$136.77	$136.75	$136.80
Purchase #4	$7.35	6.359%	$7.8174	$7.82	$7.80	$7.80
Purchase #5	$229.57	5.803%	$242.8919	$242.89	$242.90	$242.90
Purchase #6	$196.93	7.360%	$211.424	$211.42	$211.40	$211.40
Purchase #7	$149.28	6.644%	$159.1982	$159.20	$159.20	$159.20
7 purchase totals =	$949.89		$1,018.5361	$1,018.53	$1,018.50	$1,018.60