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	$92.56	11.289%	$103.0091	$103.01	$103.00	$103.00
Purchase #2	$174.52	13.165%	$197.4956	$197.50	$197.50	$197.50
Purchase #3	$35.86	8.441%	$38.8869	$38.89	$38.90	$38.90
Purchase #4	$106.82	4.438%	$111.5607	$111.56	$111.55	$111.60
Purchase #5	$158.48	6.110%	$168.1631	$168.16	$168.15	$168.20
Purchase #6	$219.65	12.451%	$246.9986	$247.00	$247.00	$247.00
Purchase #7	$136.81	4.386%	$142.8105	$142.81	$142.80	$142.80
7 purchase totals =	$924.70		$1,008.9245	$1,008.93	$1,008.90	$1,009.00