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	$226.96	3.290%	$234.427	$234.43	$234.45	$234.40
Purchase #2	$104.31	13.563%	$118.4576	$118.46	$118.45	$118.50
Purchase #3	$146.46	8.820%	$159.3778	$159.38	$159.40	$159.40
Purchase #4	$223.59	9.670%	$245.2112	$245.21	$245.20	$245.20
Purchase #5	$7.54	4.710%	$7.8951	$7.90	$7.90	$7.90
Purchase #6	$162.36	5.664%	$171.5561	$171.56	$171.55	$171.60
Purchase #7	$104.31	11.105%	$115.8936	$115.89	$115.90	$115.90
7 purchase totals =	$975.53		$1,052.8184	$1,052.83	$1,052.85	$1,052.90