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	$165.76	3.575%	$171.6859	$171.69	$171.70	$171.70
Purchase #2	$110.93	6.336%	$117.9585	$117.96	$117.95	$118.00
Purchase #3	$45.27	8.789%	$49.2488	$49.25	$49.25	$49.20
Purchase #4	$245.94	10.262%	$271.1784	$271.18	$271.20	$271.20
Purchase #5	$98.32	13.617%	$111.7082	$111.71	$111.70	$111.70
Purchase #6	$166.60	11.531%	$185.8106	$185.81	$185.80	$185.80
Purchase #7	$113.64	6.410%	$120.9243	$120.92	$120.90	$120.90
7 purchase totals =	$946.46		$1,028.5147	$1,028.52	$1,028.50	$1,028.50