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	$63.35	6.513%	$67.476	$67.48	$67.50	$67.50
Purchase #2	$237.77	10.441%	$262.5956	$262.60	$262.60	$262.60
Purchase #3	$13.83	5.651%	$14.6115	$14.61	$14.60	$14.60
Purchase #4	$90.77	6.404%	$96.5829	$96.58	$96.60	$96.60
Purchase #5	$120.27	8.123%	$130.0395	$130.04	$130.05	$130.00
Purchase #6	$130.38	3.237%	$134.6004	$134.60	$134.60	$134.60
Purchase #7	$239.28	3.488%	$247.6261	$247.63	$247.65	$247.60
7 purchase totals =	$895.65		$953.5320	$953.54	$953.60	$953.50