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	$249.86	10.753%	$276.7274	$276.73	$276.75	$276.70
Purchase #2	$98.31	5.131%	$103.3543	$103.35	$103.35	$103.40
Purchase #3	$156.92	4.315%	$163.6911	$163.69	$163.70	$163.70
Purchase #4	$113.27	3.362%	$117.0781	$117.08	$117.10	$117.10
Purchase #5	$49.78	6.594%	$53.0625	$53.06	$53.05	$53.10
Purchase #6	$150.61	11.277%	$167.5943	$167.59	$167.60	$167.60
Purchase #7	$114.48	8.119%	$123.7746	$123.77	$123.75	$123.80
7 purchase totals =	$933.23		$1,005.2823	$1,005.27	$1,005.30	$1,005.40