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	$134.87	5.846%	$142.7545	$142.75	$142.75	$142.80
Purchase #2	$64.58	11.764%	$72.1772	$72.18	$72.20	$72.20
Purchase #3	$8.42	12.828%	$9.5001	$9.50	$9.50	$9.50
Purchase #4	$205.78	8.763%	$223.8125	$223.81	$223.80	$223.80
Purchase #5	$221.69	12.429%	$249.2439	$249.24	$249.25	$249.20
Purchase #6	$98.56	6.803%	$105.265	$105.27	$105.25	$105.30
Purchase #7	$227.48	11.321%	$253.233	$253.23	$253.25	$253.20
7 purchase totals =	$961.38		$1,055.9862	$1,055.98	$1,056.00	$1,056.00