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	$245.66	7.714%	$264.6102	$264.61	$264.60	$264.60
Purchase #2	$169.78	8.170%	$183.651	$183.65	$183.65	$183.70
Purchase #3	$82.95	11.849%	$92.7787	$92.78	$92.80	$92.80
Purchase #4	$223.76	3.380%	$231.3231	$231.32	$231.30	$231.30
Purchase #5	$70.87	11.379%	$78.9343	$78.93	$78.95	$78.90
Purchase #6	$37.65	10.140%	$41.4677	$41.47	$41.45	$41.50
Purchase #7	$46.59	10.150%	$51.3189	$51.32	$51.30	$51.30
7 purchase totals =	$877.26		$944.0839	$944.08	$944.05	$944.10