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	$214.44	6.627%	$228.6509	$228.65	$228.65	$228.70
Purchase #2	$78.40	9.430%	$85.7931	$85.79	$85.80	$85.80
Purchase #3	$67.86	7.255%	$72.7832	$72.78	$72.80	$72.80
Purchase #4	$105.92	3.363%	$109.4821	$109.48	$109.50	$109.50
Purchase #5	$88.46	12.750%	$99.7387	$99.74	$99.75	$99.70
Purchase #6	$17.59	6.308%	$18.6996	$18.70	$18.70	$18.70
Purchase #7	$124.73	4.794%	$130.7096	$130.71	$130.70	$130.70
7 purchase totals =	$697.40		$745.8572	$745.85	$745.90	$745.90