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	$105.35	5.136%	$110.7608	$110.76	$110.75	$110.80
Purchase #2	$36.62	9.544%	$40.115	$40.12	$40.10	$40.10
Purchase #3	$36.47	11.322%	$40.5991	$40.60	$40.60	$40.60
Purchase #4	$168.61	13.223%	$190.9053	$190.91	$190.90	$190.90
Purchase #5	$163.30	5.162%	$171.7295	$171.73	$171.75	$171.70
Purchase #6	$229.90	6.643%	$245.1723	$245.17	$245.15	$245.20
Purchase #7	$183.72	12.465%	$206.6207	$206.62	$206.60	$206.60
7 purchase totals =	$923.97		$1,005.9027	$1,005.91	$1,005.85	$1,005.90