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	$243.30	9.153%	$265.5692	$265.57	$265.55	$265.60
Purchase #2	$52.97	11.412%	$59.0149	$59.01	$59.00	$59.00
Purchase #3	$23.89	5.118%	$25.1127	$25.11	$25.10	$25.10
Purchase #4	$223.87	13.857%	$254.8917	$254.89	$254.90	$254.90
Purchase #5	$95.44	4.642%	$99.8703	$99.87	$99.85	$99.90
Purchase #6	$151.83	10.187%	$167.2969	$167.30	$167.30	$167.30
Purchase #7	$26.87	7.456%	$28.8734	$28.87	$28.85	$28.90
7 purchase totals =	$818.17		$900.6291	$900.62	$900.55	$900.70