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	$165.81	11.776%	$185.3358	$185.34	$185.35	$185.30
Purchase #2	$91.45	8.280%	$99.0221	$99.02	$99.00	$99.00
Purchase #3	$191.38	8.116%	$206.9124	$206.91	$206.90	$206.90
Purchase #4	$156.54	8.418%	$169.7175	$169.72	$169.70	$169.70
Purchase #5	$41.85	9.662%	$45.8935	$45.89	$45.90	$45.90
Purchase #6	$144.68	5.113%	$152.0775	$152.08	$152.10	$152.10
Purchase #7	$173.50	10.380%	$191.5093	$191.51	$191.50	$191.50
7 purchase totals =	$965.21		$1,050.4681	$1,050.47	$1,050.45	$1,050.40