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	$244.42	4.676%	$255.8491	$255.85	$255.85	$255.80
Purchase #2	$32.96	7.236%	$35.345	$35.35	$35.35	$35.30
Purchase #3	$19.39	13.673%	$22.0412	$22.04	$22.05	$22.00
Purchase #4	$174.99	13.780%	$199.1036	$199.10	$199.10	$199.10
Purchase #5	$250.30	3.742%	$259.6662	$259.67	$259.65	$259.70
Purchase #6	$135.43	4.490%	$141.5108	$141.51	$141.50	$141.50
Purchase #7	$165.85	12.515%	$186.6061	$186.61	$186.60	$186.60
7 purchase totals =	$1,023.34		$1,100.1220	$1,100.13	$1,100.10	$1,100.00