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	$192.57	5.584%	$203.3231	$203.32	$203.30	$203.30
Purchase #2	$209.29	9.702%	$229.5953	$229.60	$229.60	$229.60
Purchase #3	$85.86	7.467%	$92.2712	$92.27	$92.25	$92.30
Purchase #4	$67.88	7.416%	$72.914	$72.91	$72.90	$72.90
Purchase #5	$167.61	10.462%	$185.1454	$185.15	$185.15	$185.10
Purchase #6	$222.89	11.541%	$248.6137	$248.61	$248.60	$248.60
Purchase #7	$51.32	4.305%	$53.5293	$53.53	$53.55	$53.50
7 purchase totals =	$997.42		$1,085.3920	$1,085.39	$1,085.35	$1,085.30