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	$56.57	4.476%	$59.1021	$59.10	$59.10	$59.10
Purchase #2	$128.39	4.687%	$134.4076	$134.41	$134.40	$134.40
Purchase #3	$59.80	5.758%	$63.2433	$63.24	$63.25	$63.20
Purchase #4	$212.61	9.473%	$232.7505	$232.75	$232.75	$232.80
Purchase #5	$59.86	3.111%	$61.7222	$61.72	$61.70	$61.70
Purchase #6	$50.26	9.280%	$54.9241	$54.92	$54.90	$54.90
Purchase #7	$103.61	13.154%	$117.2389	$117.24	$117.25	$117.20
7 purchase totals =	$671.10		$723.3887	$723.38	$723.35	$723.30