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	$177.74	4.575%	$185.8716	$185.87	$185.85	$185.90
Purchase #2	$85.76	6.632%	$91.4476	$91.45	$91.45	$91.40
Purchase #3	$85.73	5.129%	$90.1271	$90.13	$90.15	$90.10
Purchase #4	$219.50	6.160%	$233.0212	$233.02	$233.00	$233.00
Purchase #5	$41.64	9.227%	$45.4821	$45.48	$45.50	$45.50
Purchase #6	$10.83	4.376%	$11.3039	$11.30	$11.30	$11.30
Purchase #7	$133.52	11.800%	$149.2754	$149.28	$149.30	$149.30
7 purchase totals =	$754.72		$806.5289	$806.53	$806.55	$806.50