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	$241.87	5.266%	$254.6069	$254.61	$254.60	$254.60
Purchase #2	$18.27	7.794%	$19.694	$19.69	$19.70	$19.70
Purchase #3	$92.92	5.712%	$98.2276	$98.23	$98.25	$98.20
Purchase #4	$195.72	8.329%	$212.0215	$212.02	$212.00	$212.00
Purchase #5	$191.50	10.457%	$211.5252	$211.53	$211.55	$211.50
Purchase #6	$131.89	4.528%	$137.862	$137.86	$137.85	$137.90
Purchase #7	$116.61	12.483%	$131.1664	$131.17	$131.15	$131.20
7 purchase totals =	$988.78		$1,065.1036	$1,065.11	$1,065.10	$1,065.10