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	$92.47	6.439%	$98.4241	$98.42	$98.40	$98.40
Purchase #2	$136.34	11.280%	$151.7192	$151.72	$151.70	$151.70
Purchase #3	$185.50	5.805%	$196.2683	$196.27	$196.25	$196.30
Purchase #4	$56.55	5.546%	$59.6863	$59.69	$59.70	$59.70
Purchase #5	$175.45	13.483%	$199.1059	$199.11	$199.10	$199.10
Purchase #6	$28.92	6.440%	$30.7824	$30.78	$30.80	$30.80
Purchase #7	$7.35	8.227%	$7.9547	$7.95	$7.95	$8.00
7 purchase totals =	$682.58		$743.9409	$743.94	$743.90	$744.00