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	$185.58	3.226%	$191.5668	$191.57	$191.55	$191.60
Purchase #2	$84.28	10.729%	$93.3224	$93.32	$93.30	$93.30
Purchase #3	$69.89	3.564%	$72.3809	$72.38	$72.40	$72.40
Purchase #4	$185.53	12.599%	$208.9049	$208.90	$208.90	$208.90
Purchase #5	$44.30	13.215%	$50.1542	$50.15	$50.15	$50.20
Purchase #6	$101.89	10.120%	$112.2013	$112.20	$112.20	$112.20
Purchase #7	$172.82	6.747%	$184.4802	$184.48	$184.50	$184.50
7 purchase totals =	$844.29		$913.0107	$913.00	$913.00	$913.10