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	$58.69	12.256%	$65.883	$65.88	$65.90	$65.90
Purchase #2	$135.80	10.468%	$150.0155	$150.02	$150.00	$150.00
Purchase #3	$150.87	7.127%	$161.6225	$161.62	$161.60	$161.60
Purchase #4	$151.78	11.123%	$168.6625	$168.66	$168.65	$168.70
Purchase #5	$249.50	13.280%	$282.6336	$282.63	$282.65	$282.60
Purchase #6	$85.53	11.222%	$95.1282	$95.13	$95.15	$95.10
Purchase #7	$81.42	9.282%	$88.9774	$88.98	$89.00	$89.00
7 purchase totals =	$913.59		$1,012.9227	$1,012.92	$1,012.95	$1,012.90