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	$170.61	8.773%	$185.5776	$185.58	$185.60	$185.60
Purchase #2	$11.67	10.483%	$12.8934	$12.89	$12.90	$12.90
Purchase #3	$91.38	13.339%	$103.5692	$103.57	$103.55	$103.60
Purchase #4	$67.31	7.773%	$72.542	$72.54	$72.55	$72.50
Purchase #5	$69.38	10.637%	$76.76	$76.76	$76.75	$76.80
Purchase #6	$128.76	10.405%	$142.1575	$142.16	$142.15	$142.20
Purchase #7	$175.28	11.518%	$195.4688	$195.47	$195.45	$195.50
7 purchase totals =	$714.39		$788.9685	$788.97	$788.95	$789.10