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	$181.82	9.254%	$198.6456	$198.65	$198.65	$198.60
Purchase #2	$85.50	12.665%	$96.3286	$96.33	$96.35	$96.30
Purchase #3	$101.69	10.303%	$112.1671	$112.17	$112.15	$112.20
Purchase #4	$12.45	11.548%	$13.8877	$13.89	$13.90	$13.90
Purchase #5	$13.86	6.528%	$14.7648	$14.76	$14.75	$14.80
Purchase #6	$197.98	7.718%	$213.2601	$213.26	$213.25	$213.30
Purchase #7	$53.41	10.640%	$59.0928	$59.09	$59.10	$59.10
7 purchase totals =	$646.71		$708.1467	$708.15	$708.15	$708.20