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	$59.40	10.398%	$65.5764	$65.58	$65.60	$65.60
Purchase #2	$119.38	3.793%	$123.9081	$123.91	$123.90	$123.90
Purchase #3	$65.35	12.643%	$73.6122	$73.61	$73.60	$73.60
Purchase #4	$25.44	3.805%	$26.408	$26.41	$26.40	$26.40
Purchase #5	$183.35	5.486%	$193.4086	$193.41	$193.40	$193.40
Purchase #6	$180.98	8.635%	$196.6076	$196.61	$196.60	$196.60
Purchase #7	$39.61	10.216%	$43.6566	$43.66	$43.65	$43.70
7 purchase totals =	$673.51		$723.1775	$723.19	$723.15	$723.20