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	$89.45	7.206%	$95.8958	$95.90	$95.90	$95.90
Purchase #2	$240.31	9.365%	$262.815	$262.82	$262.80	$262.80
Purchase #3	$48.36	3.171%	$49.8935	$49.89	$49.90	$49.90
Purchase #4	$215.73	3.723%	$223.7616	$223.76	$223.75	$223.80
Purchase #5	$232.78	6.460%	$247.8176	$247.82	$247.80	$247.80
Purchase #6	$34.57	8.123%	$37.3781	$37.38	$37.40	$37.40
Purchase #7	$202.94	4.686%	$212.4498	$212.45	$212.45	$212.40
7 purchase totals =	$1,064.14		$1,130.0114	$1,130.02	$1,130.00	$1,130.00