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	$176.68	5.610%	$186.5917	$186.59	$186.60	$186.60
Purchase #2	$174.55	12.515%	$196.3949	$196.39	$196.40	$196.40
Purchase #3	$185.27	13.446%	$210.1814	$210.18	$210.20	$210.20
Purchase #4	$116.73	6.668%	$124.5136	$124.51	$124.50	$124.50
Purchase #5	$90.57	6.144%	$96.1346	$96.13	$96.15	$96.10
Purchase #6	$91.71	8.157%	$99.1908	$99.19	$99.20	$99.20
Purchase #7	$225.93	7.634%	$243.1775	$243.18	$243.20	$243.20
7 purchase totals =	$1,061.44		$1,156.1845	$1,156.17	$1,156.25	$1,156.20