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	$182.98	3.637%	$189.635	$189.64	$189.65	$189.60
Purchase #2	$154.33	11.700%	$172.3866	$172.39	$172.40	$172.40
Purchase #3	$183.73	3.366%	$189.9144	$189.91	$189.90	$189.90
Purchase #4	$76.87	4.763%	$80.5313	$80.53	$80.55	$80.50
Purchase #5	$134.67	12.715%	$151.7933	$151.79	$151.80	$151.80
Purchase #6	$155.33	12.264%	$174.3797	$174.38	$174.40	$174.40
Purchase #7	$190.93	8.488%	$207.1361	$207.14	$207.15	$207.10
7 purchase totals =	$1,078.84		$1,165.7764	$1,165.78	$1,165.85	$1,165.70