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	$84.89	11.780%	$94.89	$94.89	$94.90	$94.90
Purchase #2	$182.52	6.769%	$194.8748	$194.87	$194.85	$194.90
Purchase #3	$37.73	13.154%	$42.693	$42.69	$42.70	$42.70
Purchase #4	$212.30	11.697%	$237.1327	$237.13	$237.15	$237.10
Purchase #5	$44.71	10.393%	$49.3567	$49.36	$49.35	$49.40
Purchase #6	$17.88	8.199%	$19.346	$19.35	$19.35	$19.30
Purchase #7	$176.69	3.300%	$182.5208	$182.52	$182.50	$182.50
7 purchase totals =	$756.72		$820.8140	$820.81	$820.80	$820.80