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	$66.33	8.805%	$72.1704	$72.17	$72.15	$72.20
Purchase #2	$223.75	8.866%	$243.5877	$243.59	$243.60	$243.60
Purchase #3	$154.99	8.129%	$167.5891	$167.59	$167.60	$167.60
Purchase #4	$232.68	4.751%	$243.7346	$243.73	$243.75	$243.70
Purchase #5	$99.89	5.597%	$105.4808	$105.48	$105.50	$105.50
Purchase #6	$60.66	10.419%	$66.9802	$66.98	$67.00	$67.00
Purchase #7	$229.62	5.686%	$242.6762	$242.68	$242.70	$242.70
7 purchase totals =	$1,067.92		$1,142.2190	$1,142.22	$1,142.30	$1,142.30