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	$188.53	10.419%	$208.1729	$208.17	$208.15	$208.20
Purchase #2	$60.97	6.336%	$64.8331	$64.83	$64.85	$64.80
Purchase #3	$213.86	9.632%	$234.459	$234.46	$234.45	$234.50
Purchase #4	$196.57	13.692%	$223.4844	$223.48	$223.50	$223.50
Purchase #5	$85.48	3.860%	$88.7795	$88.78	$88.80	$88.80
Purchase #6	$210.64	3.554%	$218.1261	$218.13	$218.15	$218.10
Purchase #7	$41.80	8.102%	$45.1866	$45.19	$45.20	$45.20
7 purchase totals =	$997.85		$1,083.0416	$1,083.04	$1,083.10	$1,083.10