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	$234.33	8.301%	$253.7817	$253.78	$253.80	$253.80
Purchase #2	$226.52	13.347%	$256.7536	$256.75	$256.75	$256.80
Purchase #3	$187.53	10.735%	$207.6613	$207.66	$207.65	$207.70
Purchase #4	$41.59	11.177%	$46.2385	$46.24	$46.25	$46.20
Purchase #5	$152.80	10.315%	$168.5613	$168.56	$168.55	$168.60
Purchase #6	$5.78	9.156%	$6.3092	$6.31	$6.30	$6.30
Purchase #7	$86.34	3.364%	$89.2445	$89.24	$89.25	$89.20
7 purchase totals =	$934.89		$1,028.5501	$1,028.54	$1,028.55	$1,028.60