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	$158.49	6.384%	$168.608	$168.61	$168.60	$168.60
Purchase #2	$133.27	10.766%	$147.6178	$147.62	$147.60	$147.60
Purchase #3	$225.91	5.549%	$238.4457	$238.45	$238.45	$238.40
Purchase #4	$45.58	10.701%	$50.4575	$50.46	$50.45	$50.50
Purchase #5	$69.60	12.662%	$78.4128	$78.41	$78.40	$78.40
Purchase #6	$95.48	13.736%	$108.5951	$108.60	$108.60	$108.60
Purchase #7	$243.58	7.582%	$262.0482	$262.05	$262.05	$262.00
7 purchase totals =	$971.91		$1,054.1851	$1,054.20	$1,054.15	$1,054.10