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	$187.76	4.598%	$196.3932	$196.39	$196.40	$196.40
Purchase #2	$71.45	10.498%	$78.9508	$78.95	$78.95	$79.00
Purchase #3	$82.25	3.762%	$85.3442	$85.34	$85.35	$85.30
Purchase #4	$195.53	6.696%	$208.6227	$208.62	$208.60	$208.60
Purchase #5	$55.76	8.771%	$60.6507	$60.65	$60.65	$60.70
Purchase #6	$155.92	6.722%	$166.4009	$166.40	$166.40	$166.40
Purchase #7	$20.44	7.401%	$21.9528	$21.95	$21.95	$22.00
7 purchase totals =	$769.11		$818.3153	$818.30	$818.30	$818.40