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	$65.67	10.843%	$72.7906	$72.79	$72.80	$72.80
Purchase #2	$216.72	7.115%	$232.1396	$232.14	$232.15	$232.10
Purchase #3	$249.32	6.127%	$264.5958	$264.60	$264.60	$264.60
Purchase #4	$129.87	13.197%	$147.0089	$147.01	$147.00	$147.00
Purchase #5	$111.94	10.113%	$123.2605	$123.26	$123.25	$123.30
Purchase #6	$106.59	5.758%	$112.7275	$112.73	$112.75	$112.70
Purchase #7	$82.74	8.811%	$90.0302	$90.03	$90.05	$90.00
7 purchase totals =	$962.85		$1,042.5531	$1,042.56	$1,042.60	$1,042.50