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	$196.89	9.663%	$215.9155	$215.92	$215.90	$215.90
Purchase #2	$86.73	3.730%	$89.965	$89.97	$89.95	$90.00
Purchase #3	$92.81	3.210%	$95.7892	$95.79	$95.80	$95.80
Purchase #4	$189.88	11.697%	$212.0903	$212.09	$212.10	$212.10
Purchase #5	$249.96	7.181%	$267.9096	$267.91	$267.90	$267.90
Purchase #6	$56.72	10.297%	$62.5605	$62.56	$62.55	$62.60
Purchase #7	$169.82	9.834%	$186.5201	$186.52	$186.50	$186.50
7 purchase totals =	$1,042.81		$1,130.7502	$1,130.76	$1,130.70	$1,130.80