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	$86.53	11.399%	$96.3936	$96.39	$96.40	$96.40
Purchase #2	$184.52	3.330%	$190.6645	$190.66	$190.65	$190.70
Purchase #3	$166.54	5.144%	$175.1068	$175.11	$175.10	$175.10
Purchase #4	$70.32	8.413%	$76.236	$76.24	$76.25	$76.20
Purchase #5	$110.99	11.590%	$123.8537	$123.85	$123.85	$123.90
Purchase #6	$101.90	3.846%	$105.8191	$105.82	$105.80	$105.80
Purchase #7	$12.28	10.464%	$13.565	$13.57	$13.55	$13.60
7 purchase totals =	$733.08		$781.6387	$781.64	$781.60	$781.70