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	$9.90	4.661%	$10.3614	$10.36	$10.35	$10.40
Purchase #2	$86.92	10.209%	$95.7937	$95.79	$95.80	$95.80
Purchase #3	$57.64	3.474%	$59.6424	$59.64	$59.65	$59.60
Purchase #4	$219.85	4.408%	$229.541	$229.54	$229.55	$229.50
Purchase #5	$76.30	7.842%	$82.2834	$82.28	$82.30	$82.30
Purchase #6	$189.91	8.298%	$205.6687	$205.67	$205.65	$205.70
Purchase #7	$30.76	8.866%	$33.4872	$33.49	$33.50	$33.50
7 purchase totals =	$671.28		$716.7778	$716.77	$716.80	$716.80