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	$151.77	10.229%	$167.2946	$167.29	$167.30	$167.30
Purchase #2	$33.64	11.611%	$37.5459	$37.55	$37.55	$37.50
Purchase #3	$87.43	3.842%	$90.7891	$90.79	$90.80	$90.80
Purchase #4	$152.86	3.229%	$157.7958	$157.80	$157.80	$157.80
Purchase #5	$242.88	8.360%	$263.1848	$263.18	$263.20	$263.20
Purchase #6	$222.80	12.641%	$250.9641	$250.96	$250.95	$251.00
Purchase #7	$42.62	12.110%	$47.7813	$47.78	$47.80	$47.80
7 purchase totals =	$934.00		$1,015.3556	$1,015.35	$1,015.40	$1,015.40