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	$79.78	5.659%	$84.2948	$84.29	$84.30	$84.30
Purchase #2	$88.92	12.871%	$100.3649	$100.36	$100.35	$100.40
Purchase #3	$140.39	3.293%	$145.013	$145.01	$145.00	$145.00
Purchase #4	$68.61	4.777%	$71.8875	$71.89	$71.90	$71.90
Purchase #5	$127.46	6.820%	$136.1528	$136.15	$136.15	$136.20
Purchase #6	$115.82	6.773%	$123.6645	$123.66	$123.65	$123.70
Purchase #7	$235.25	7.655%	$253.2584	$253.26	$253.25	$253.30
7 purchase totals =	$856.23		$914.6359	$914.62	$914.60	$914.80