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	$183.70	12.292%	$206.2804	$206.28	$206.30	$206.30
Purchase #2	$220.49	10.173%	$242.9204	$242.92	$242.90	$242.90
Purchase #3	$59.76	9.545%	$65.4641	$65.46	$65.45	$65.50
Purchase #4	$6.76	10.613%	$7.4774	$7.48	$7.50	$7.50
Purchase #5	$244.64	11.672%	$273.1944	$273.19	$273.20	$273.20
Purchase #6	$157.33	5.192%	$165.4986	$165.50	$165.50	$165.50
Purchase #7	$46.33	9.135%	$50.5622	$50.56	$50.55	$50.60
7 purchase totals =	$919.01		$1,011.3975	$1,011.39	$1,011.40	$1,011.50