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	$123.73	8.570%	$134.3337	$134.33	$134.35	$134.30
Purchase #2	$57.32	8.151%	$61.9922	$61.99	$62.00	$62.00
Purchase #3	$40.66	4.722%	$42.58	$42.58	$42.60	$42.60
Purchase #4	$133.71	10.369%	$147.5744	$147.57	$147.55	$147.60
Purchase #5	$80.25	12.298%	$90.1191	$90.12	$90.10	$90.10
Purchase #6	$159.63	4.433%	$166.7064	$166.71	$166.70	$166.70
Purchase #7	$197.57	4.479%	$206.4192	$206.42	$206.40	$206.40
7 purchase totals =	$792.87		$849.7250	$849.72	$849.70	$849.70