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	$75.85	8.618%	$82.3868	$82.39	$82.40	$82.40
Purchase #2	$69.46	9.664%	$76.1726	$76.17	$76.15	$76.20
Purchase #3	$144.26	4.874%	$151.2912	$151.29	$151.30	$151.30
Purchase #4	$128.84	10.337%	$142.1582	$142.16	$142.15	$142.20
Purchase #5	$9.89	3.860%	$10.2718	$10.27	$10.25	$10.30
Purchase #6	$42.26	7.715%	$45.5204	$45.52	$45.50	$45.50
Purchase #7	$231.37	5.247%	$243.51	$243.51	$243.50	$243.50
7 purchase totals =	$701.93		$751.3110	$751.31	$751.25	$751.40