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	$225.69	5.490%	$238.0804	$238.08	$238.10	$238.10
Purchase #2	$161.27	10.761%	$178.6243	$178.62	$178.60	$178.60
Purchase #3	$240.72	12.843%	$271.6357	$271.64	$271.65	$271.60
Purchase #4	$208.84	13.173%	$236.3505	$236.35	$236.35	$236.40
Purchase #5	$107.97	6.407%	$114.8876	$114.89	$114.90	$114.90
Purchase #6	$30.29	8.686%	$32.921	$32.92	$32.90	$32.90
Purchase #7	$35.33	9.822%	$38.8001	$38.80	$38.80	$38.80
7 purchase totals =	$1,010.11		$1,111.2996	$1,111.30	$1,111.30	$1,111.30