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	$176.85	11.300%	$196.8341	$196.83	$196.85	$196.80
Purchase #2	$101.89	5.206%	$107.1944	$107.19	$107.20	$107.20
Purchase #3	$180.53	5.250%	$190.0078	$190.01	$190.00	$190.00
Purchase #4	$75.90	4.167%	$79.0628	$79.06	$79.05	$79.10
Purchase #5	$41.88	6.352%	$44.5402	$44.54	$44.55	$44.50
Purchase #6	$84.79	5.687%	$89.612	$89.61	$89.60	$89.60
Purchase #7	$37.99	12.722%	$42.8231	$42.82	$42.80	$42.80
7 purchase totals =	$699.83		$750.0744	$750.06	$750.05	$750.00