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	$149.39	13.427%	$169.4486	$169.45	$169.45	$169.40
Purchase #2	$143.90	4.570%	$150.4762	$150.48	$150.50	$150.50
Purchase #3	$105.82	9.506%	$115.8792	$115.88	$115.90	$115.90
Purchase #4	$134.83	12.486%	$151.6649	$151.66	$151.65	$151.70
Purchase #5	$150.91	5.269%	$158.8614	$158.86	$158.85	$158.90
Purchase #6	$240.84	8.595%	$261.5402	$261.54	$261.55	$261.50
Purchase #7	$68.33	7.344%	$73.3482	$73.35	$73.35	$73.30
7 purchase totals =	$994.02		$1,081.2187	$1,081.22	$1,081.25	$1,081.20