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	$55.46	12.259%	$62.2588	$62.26	$62.25	$62.30
Purchase #2	$175.73	6.499%	$187.1507	$187.15	$187.15	$187.20
Purchase #3	$94.35	10.339%	$104.1048	$104.10	$104.10	$104.10
Purchase #4	$119.86	3.134%	$123.6164	$123.62	$123.60	$123.60
Purchase #5	$80.69	6.143%	$85.6468	$85.65	$85.65	$85.60
Purchase #6	$203.88	3.141%	$210.2839	$210.28	$210.30	$210.30
Purchase #7	$41.46	9.742%	$45.499	$45.50	$45.50	$45.50
7 purchase totals =	$771.43		$818.5604	$818.56	$818.55	$818.60