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	$52.33	3.748%	$54.2913	$54.29	$54.30	$54.30
Purchase #2	$250.46	6.316%	$266.2791	$266.28	$266.30	$266.30
Purchase #3	$219.74	5.341%	$231.4763	$231.48	$231.50	$231.50
Purchase #4	$166.45	10.744%	$184.3334	$184.33	$184.35	$184.30
Purchase #5	$192.44	3.321%	$198.8309	$198.83	$198.85	$198.80
Purchase #6	$126.53	3.726%	$131.2445	$131.24	$131.25	$131.20
Purchase #7	$17.91	12.294%	$20.1119	$20.11	$20.10	$20.10
7 purchase totals =	$1,025.86		$1,086.5674	$1,086.56	$1,086.65	$1,086.50