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	$215.61	5.232%	$226.8907	$226.89	$226.90	$226.90
Purchase #2	$78.29	13.633%	$88.9633	$88.96	$88.95	$89.00
Purchase #3	$6.29	9.499%	$6.8875	$6.89	$6.90	$6.90
Purchase #4	$200.83	11.326%	$223.576	$223.58	$223.60	$223.60
Purchase #5	$96.56	13.312%	$109.4141	$109.41	$109.40	$109.40
Purchase #6	$39.84	7.406%	$42.7906	$42.79	$42.80	$42.80
Purchase #7	$161.76	12.829%	$182.5122	$182.51	$182.50	$182.50
7 purchase totals =	$799.18		$881.0344	$881.03	$881.05	$881.10