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	$130.53	7.756%	$140.6539	$140.65	$140.65	$140.70
Purchase #2	$96.98	11.342%	$107.9795	$107.98	$108.00	$108.00
Purchase #3	$85.51	4.700%	$89.529	$89.53	$89.55	$89.50
Purchase #4	$189.89	9.839%	$208.5733	$208.57	$208.55	$208.60
Purchase #5	$177.75	6.799%	$189.8352	$189.84	$189.85	$189.80
Purchase #6	$221.46	9.328%	$242.1178	$242.12	$242.10	$242.10
Purchase #7	$79.92	6.853%	$85.3969	$85.40	$85.40	$85.40
7 purchase totals =	$982.04		$1,064.0856	$1,064.09	$1,064.10	$1,064.10