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	$57.25	11.317%	$63.729	$63.73	$63.75	$63.70
Purchase #2	$126.46	6.579%	$134.7798	$134.78	$134.80	$134.80
Purchase #3	$185.29	3.269%	$191.3471	$191.35	$191.35	$191.30
Purchase #4	$68.59	5.661%	$72.4729	$72.47	$72.45	$72.50
Purchase #5	$183.61	12.659%	$206.8532	$206.85	$206.85	$206.90
Purchase #6	$24.75	13.618%	$28.1205	$28.12	$28.10	$28.10
Purchase #7	$211.37	5.430%	$222.8474	$222.85	$222.85	$222.80
7 purchase totals =	$857.32		$920.1499	$920.15	$920.15	$920.10