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	$202.85	9.675%	$222.4757	$222.48	$222.50	$222.50
Purchase #2	$42.70	7.376%	$45.8496	$45.85	$45.85	$45.80
Purchase #3	$167.48	9.820%	$183.9265	$183.93	$183.95	$183.90
Purchase #4	$230.66	7.212%	$247.2952	$247.30	$247.30	$247.30
Purchase #5	$77.86	10.742%	$86.2237	$86.22	$86.20	$86.20
Purchase #6	$86.86	11.136%	$96.5327	$96.53	$96.55	$96.50
Purchase #7	$118.70	10.408%	$131.0543	$131.05	$131.05	$131.10
7 purchase totals =	$927.11		$1,013.3577	$1,013.36	$1,013.40	$1,013.30