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	$241.83	11.614%	$269.9161	$269.92	$269.90	$269.90
Purchase #2	$221.83	12.448%	$249.4434	$249.44	$249.45	$249.40
Purchase #3	$92.61	7.686%	$99.728	$99.73	$99.75	$99.70
Purchase #4	$58.91	11.502%	$65.6858	$65.69	$65.70	$65.70
Purchase #5	$89.46	11.654%	$99.8857	$99.89	$99.90	$99.90
Purchase #6	$101.40	3.182%	$104.6265	$104.63	$104.65	$104.60
Purchase #7	$189.81	5.821%	$200.8588	$200.86	$200.85	$200.90
7 purchase totals =	$995.85		$1,090.1443	$1,090.16	$1,090.20	$1,090.10