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	$110.72	5.250%	$116.5328	$116.53	$116.55	$116.50
Purchase #2	$95.59	9.841%	$104.997	$105.00	$105.00	$105.00
Purchase #3	$148.92	9.233%	$162.6698	$162.67	$162.65	$162.70
Purchase #4	$160.83	11.790%	$179.7919	$179.79	$179.80	$179.80
Purchase #5	$142.98	5.120%	$150.3006	$150.30	$150.30	$150.30
Purchase #6	$203.84	12.479%	$229.2772	$229.28	$229.30	$229.30
Purchase #7	$216.50	8.521%	$234.948	$234.95	$234.95	$234.90
7 purchase totals =	$1,079.38		$1,178.5173	$1,178.52	$1,178.55	$1,178.50