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	$143.52	13.120%	$162.3498	$162.35	$162.35	$162.30
Purchase #2	$194.38	6.423%	$206.865	$206.87	$206.85	$206.90
Purchase #3	$244.51	11.779%	$273.3108	$273.31	$273.30	$273.30
Purchase #4	$54.86	8.542%	$59.5461	$59.55	$59.55	$59.50
Purchase #5	$16.28	9.538%	$17.8328	$17.83	$17.85	$17.80
Purchase #6	$250.90	3.411%	$259.4582	$259.46	$259.45	$259.50
Purchase #7	$154.83	6.723%	$165.2392	$165.24	$165.25	$165.20
7 purchase totals =	$1,059.28		$1,144.6019	$1,144.61	$1,144.60	$1,144.50