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	$152.77	6.470%	$162.6542	$162.65	$162.65	$162.70
Purchase #2	$37.32	11.464%	$41.5984	$41.60	$41.60	$41.60
Purchase #3	$74.55	8.149%	$80.6251	$80.63	$80.65	$80.60
Purchase #4	$92.38	3.132%	$95.2733	$95.27	$95.25	$95.30
Purchase #5	$93.69	10.484%	$103.5125	$103.51	$103.50	$103.50
Purchase #6	$24.97	5.505%	$26.3446	$26.34	$26.35	$26.30
Purchase #7	$188.33	4.466%	$196.7408	$196.74	$196.75	$196.70
7 purchase totals =	$664.01		$706.7489	$706.74	$706.75	$706.70