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	$169.73	11.717%	$189.6173	$189.62	$189.60	$189.60
Purchase #2	$232.64	13.311%	$263.6067	$263.61	$263.60	$263.60
Purchase #3	$73.59	6.404%	$78.3027	$78.30	$78.30	$78.30
Purchase #4	$170.76	9.479%	$186.9463	$186.95	$186.95	$186.90
Purchase #5	$122.46	13.103%	$138.5059	$138.51	$138.50	$138.50
Purchase #6	$166.91	9.387%	$182.5778	$182.58	$182.60	$182.60
Purchase #7	$125.62	9.337%	$137.3491	$137.35	$137.35	$137.30
7 purchase totals =	$1,061.71		$1,176.9058	$1,176.92	$1,176.90	$1,176.80