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	$168.61	13.118%	$190.7283	$190.73	$190.75	$190.70
Purchase #2	$70.81	10.292%	$78.0978	$78.10	$78.10	$78.10
Purchase #3	$221.55	8.578%	$240.5546	$240.55	$240.55	$240.60
Purchase #4	$238.61	12.829%	$269.2213	$269.22	$269.20	$269.20
Purchase #5	$131.79	7.128%	$141.184	$141.18	$141.20	$141.20
Purchase #6	$120.35	12.568%	$135.4756	$135.48	$135.50	$135.50
Purchase #7	$84.44	6.226%	$89.6972	$89.70	$89.70	$89.70
7 purchase totals =	$1,036.16		$1,144.9588	$1,144.96	$1,145.00	$1,145.00