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	$216.69	10.198%	$238.788	$238.79	$238.80	$238.80
Purchase #2	$91.83	13.164%	$103.9185	$103.92	$103.90	$103.90
Purchase #3	$82.96	8.618%	$90.1095	$90.11	$90.10	$90.10
Purchase #4	$187.56	12.164%	$210.3748	$210.37	$210.35	$210.40
Purchase #5	$203.99	8.783%	$221.9064	$221.91	$221.90	$221.90
Purchase #6	$76.76	3.552%	$79.4865	$79.49	$79.50	$79.50
Purchase #7	$163.59	5.318%	$172.2897	$172.29	$172.30	$172.30
7 purchase totals =	$1,023.38		$1,116.8734	$1,116.88	$1,116.85	$1,116.90