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	$64.98	3.413%	$67.1978	$67.20	$67.20	$67.20
Purchase #2	$222.44	8.245%	$240.7802	$240.78	$240.80	$240.80
Purchase #3	$213.72	5.870%	$226.2654	$226.27	$226.25	$226.30
Purchase #4	$207.84	11.186%	$231.089	$231.09	$231.10	$231.10
Purchase #5	$92.90	7.532%	$99.8972	$99.90	$99.90	$99.90
Purchase #6	$79.87	8.119%	$86.3546	$86.35	$86.35	$86.40
Purchase #7	$62.58	3.563%	$64.8097	$64.81	$64.80	$64.80
7 purchase totals =	$944.33		$1,016.3939	$1,016.40	$1,016.40	$1,016.50