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	$101.55	4.617%	$106.2386	$106.24	$106.25	$106.20
Purchase #2	$210.52	4.218%	$219.3997	$219.40	$219.40	$219.40
Purchase #3	$56.55	8.351%	$61.2725	$61.27	$61.25	$61.30
Purchase #4	$79.82	7.359%	$85.694	$85.69	$85.70	$85.70
Purchase #5	$207.66	9.550%	$227.4915	$227.49	$227.50	$227.50
Purchase #6	$81.31	12.671%	$91.6128	$91.61	$91.60	$91.60
Purchase #7	$82.64	9.663%	$90.6255	$90.63	$90.65	$90.60
7 purchase totals =	$820.05		$882.3346	$882.33	$882.35	$882.30