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	$178.88	3.707%	$185.5111	$185.51	$185.50	$185.50
Purchase #2	$178.53	9.504%	$195.4975	$195.50	$195.50	$195.50
Purchase #3	$144.44	4.789%	$151.3572	$151.36	$151.35	$151.40
Purchase #4	$66.60	11.683%	$74.3809	$74.38	$74.40	$74.40
Purchase #5	$235.68	11.809%	$263.5115	$263.51	$263.50	$263.50
Purchase #6	$43.78	8.230%	$47.3831	$47.38	$47.40	$47.40
Purchase #7	$125.57	4.402%	$131.0976	$131.10	$131.10	$131.10
7 purchase totals =	$973.48		$1,048.7389	$1,048.74	$1,048.75	$1,048.80