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	$54.97	7.572%	$59.1323	$59.13	$59.15	$59.10
Purchase #2	$79.69	11.695%	$89.0097	$89.01	$89.00	$89.00
Purchase #3	$104.85	9.333%	$114.6357	$114.64	$114.65	$114.60
Purchase #4	$97.93	8.132%	$105.8937	$105.89	$105.90	$105.90
Purchase #5	$150.52	13.847%	$171.3625	$171.36	$171.35	$171.40
Purchase #6	$170.83	9.761%	$187.5047	$187.50	$187.50	$187.50
Purchase #7	$158.34	4.393%	$165.2959	$165.30	$165.30	$165.30
7 purchase totals =	$817.13		$892.8345	$892.83	$892.85	$892.80