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	$177.96	8.406%	$192.9193	$192.92	$192.90	$192.90
Purchase #2	$131.60	12.666%	$148.2685	$148.27	$148.25	$148.30
Purchase #3	$208.69	5.479%	$220.1241	$220.12	$220.10	$220.10
Purchase #4	$25.87	6.661%	$27.5932	$27.59	$27.60	$27.60
Purchase #5	$142.84	9.738%	$156.7498	$156.75	$156.75	$156.70
Purchase #6	$79.62	3.605%	$82.4903	$82.49	$82.50	$82.50
Purchase #7	$219.72	8.587%	$238.5874	$238.59	$238.60	$238.60
7 purchase totals =	$986.30		$1,066.7326	$1,066.73	$1,066.70	$1,066.70