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	$190.25	10.556%	$210.3328	$210.33	$210.35	$210.30
Purchase #2	$80.63	11.113%	$89.5904	$89.59	$89.60	$89.60
Purchase #3	$185.32	12.575%	$208.624	$208.62	$208.60	$208.60
Purchase #4	$70.57	11.677%	$78.8105	$78.81	$78.80	$78.80
Purchase #5	$211.83	11.221%	$235.5994	$235.60	$235.60	$235.60
Purchase #6	$107.69	6.254%	$114.4249	$114.42	$114.40	$114.40
Purchase #7	$11.37	12.496%	$12.7908	$12.79	$12.80	$12.80
7 purchase totals =	$857.66		$950.1728	$950.16	$950.15	$950.10