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	$195.40	5.266%	$205.6898	$205.69	$205.70	$205.70
Purchase #2	$137.64	11.229%	$153.0956	$153.10	$153.10	$153.10
Purchase #3	$162.46	11.699%	$181.4662	$181.47	$181.45	$181.50
Purchase #4	$75.31	13.301%	$85.327	$85.33	$85.35	$85.30
Purchase #5	$154.93	10.274%	$170.8475	$170.85	$170.85	$170.80
Purchase #6	$150.65	9.734%	$165.3143	$165.31	$165.30	$165.30
Purchase #7	$182.83	12.132%	$205.0109	$205.01	$205.00	$205.00
7 purchase totals =	$1,059.22		$1,166.7513	$1,166.76	$1,166.75	$1,166.70