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	$42.88	11.456%	$47.7923	$47.79	$47.80	$47.80
Purchase #2	$37.33	6.744%	$39.8475	$39.85	$39.85	$39.80
Purchase #3	$220.69	4.683%	$231.0249	$231.02	$231.00	$231.00
Purchase #4	$68.61	5.343%	$72.2758	$72.28	$72.30	$72.30
Purchase #5	$203.55	6.400%	$216.5772	$216.58	$216.60	$216.60
Purchase #6	$229.89	8.550%	$249.5456	$249.55	$249.55	$249.50
Purchase #7	$194.97	4.851%	$204.428	$204.43	$204.45	$204.40
7 purchase totals =	$997.92		$1,061.4913	$1,061.50	$1,061.55	$1,061.40