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	$95.84	5.240%	$100.862	$100.86	$100.85	$100.90
Purchase #2	$203.90	5.869%	$215.8669	$215.87	$215.85	$215.90
Purchase #3	$23.43	12.286%	$26.3086	$26.31	$26.30	$26.30
Purchase #4	$187.96	3.281%	$194.127	$194.13	$194.15	$194.10
Purchase #5	$187.68	12.364%	$210.8848	$210.88	$210.90	$210.90
Purchase #6	$200.66	12.517%	$225.7766	$225.78	$225.80	$225.80
Purchase #7	$127.25	13.862%	$144.8894	$144.89	$144.90	$144.90
7 purchase totals =	$1,026.72		$1,118.7153	$1,118.72	$1,118.75	$1,118.80