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	$133.65	9.845%	$146.8078	$146.81	$146.80	$146.80
Purchase #2	$97.90	8.253%	$105.9797	$105.98	$106.00	$106.00
Purchase #3	$41.42	10.550%	$45.7898	$45.79	$45.80	$45.80
Purchase #4	$93.85	12.835%	$105.8956	$105.90	$105.90	$105.90
Purchase #5	$183.87	10.180%	$202.588	$202.59	$202.60	$202.60
Purchase #6	$96.73	4.326%	$100.9145	$100.91	$100.90	$100.90
Purchase #7	$59.45	11.589%	$66.3397	$66.34	$66.35	$66.30
7 purchase totals =	$706.87		$774.3151	$774.32	$774.35	$774.30