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	$128.81	10.835%	$142.7666	$142.77	$142.75	$142.80
Purchase #2	$146.72	8.531%	$159.2367	$159.24	$159.25	$159.20
Purchase #3	$212.83	11.603%	$237.5247	$237.52	$237.50	$237.50
Purchase #4	$185.63	4.476%	$193.9388	$193.94	$193.95	$193.90
Purchase #5	$227.40	7.443%	$244.3254	$244.33	$244.35	$244.30
Purchase #6	$77.87	5.811%	$82.395	$82.40	$82.40	$82.40
Purchase #7	$127.46	3.182%	$131.5158	$131.52	$131.50	$131.50
7 purchase totals =	$1,106.72		$1,191.7030	$1,191.72	$1,191.70	$1,191.60