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	$166.37	12.334%	$186.8901	$186.89	$186.90	$186.90
Purchase #2	$67.41	10.753%	$74.6586	$74.66	$74.65	$74.70
Purchase #3	$75.81	3.466%	$78.4376	$78.44	$78.45	$78.40
Purchase #4	$239.61	10.148%	$263.9256	$263.93	$263.95	$263.90
Purchase #5	$63.35	8.301%	$68.6087	$68.61	$68.60	$68.60
Purchase #6	$248.96	8.707%	$270.6369	$270.64	$270.65	$270.60
Purchase #7	$62.96	7.172%	$67.4755	$67.48	$67.50	$67.50
7 purchase totals =	$924.47		$1,010.6330	$1,010.65	$1,010.70	$1,010.60