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	$43.39	5.762%	$45.8901	$45.89	$45.90	$45.90
Purchase #2	$162.40	10.204%	$178.9713	$178.97	$178.95	$179.00
Purchase #3	$196.86	10.414%	$217.361	$217.36	$217.35	$217.40
Purchase #4	$242.41	11.508%	$270.3065	$270.31	$270.30	$270.30
Purchase #5	$96.28	13.244%	$109.0313	$109.03	$109.05	$109.00
Purchase #6	$176.62	4.380%	$184.356	$184.36	$184.35	$184.40
Purchase #7	$39.76	9.414%	$43.503	$43.50	$43.50	$43.50
7 purchase totals =	$957.72		$1,049.4192	$1,049.42	$1,049.40	$1,049.50