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	$98.81	11.107%	$109.7848	$109.78	$109.80	$109.80
Purchase #2	$157.53	6.707%	$168.0955	$168.10	$168.10	$168.10
Purchase #3	$142.34	3.611%	$147.4799	$147.48	$147.50	$147.50
Purchase #4	$141.45	10.540%	$156.3588	$156.36	$156.35	$156.40
Purchase #5	$46.64	8.191%	$50.4603	$50.46	$50.45	$50.50
Purchase #6	$215.87	13.770%	$245.5953	$245.60	$245.60	$245.60
Purchase #7	$6.29	10.364%	$6.9419	$6.94	$6.95	$6.90
7 purchase totals =	$808.93		$884.7165	$884.72	$884.75	$884.80