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	$47.31	10.704%	$52.3741	$52.37	$52.35	$52.40
Purchase #2	$139.64	11.781%	$156.091	$156.09	$156.10	$156.10
Purchase #3	$245.56	3.276%	$253.6045	$253.60	$253.60	$253.60
Purchase #4	$244.93	4.341%	$255.5624	$255.56	$255.55	$255.60
Purchase #5	$6.27	11.684%	$7.0026	$7.00	$7.00	$7.00
Purchase #6	$51.94	11.227%	$57.7713	$57.77	$57.75	$57.80
Purchase #7	$152.36	10.609%	$168.5239	$168.52	$168.50	$168.50
7 purchase totals =	$888.01		$950.9298	$950.91	$950.85	$951.00