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	$151.38	6.524%	$161.256	$161.26	$161.25	$161.30
Purchase #2	$188.35	5.510%	$198.7281	$198.73	$198.75	$198.70
Purchase #3	$112.86	3.263%	$116.5426	$116.54	$116.55	$116.50
Purchase #4	$102.50	10.569%	$113.3332	$113.33	$113.35	$113.30
Purchase #5	$65.61	7.785%	$70.7177	$70.72	$70.70	$70.70
Purchase #6	$120.75	6.231%	$128.2739	$128.27	$128.25	$128.30
Purchase #7	$196.39	8.659%	$213.3954	$213.40	$213.40	$213.40
7 purchase totals =	$937.84		$1,002.2469	$1,002.25	$1,002.25	$1,002.20