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	$82.54	6.329%	$87.764	$87.76	$87.75	$87.80
Purchase #2	$127.95	8.313%	$138.5865	$138.59	$138.60	$138.60
Purchase #3	$84.30	6.275%	$89.5898	$89.59	$89.60	$89.60
Purchase #4	$210.55	6.397%	$224.0189	$224.02	$224.00	$224.00
Purchase #5	$238.86	8.763%	$259.7913	$259.79	$259.80	$259.80
Purchase #6	$242.86	8.689%	$263.9621	$263.96	$263.95	$264.00
Purchase #7	$52.34	3.506%	$54.175	$54.18	$54.20	$54.20
7 purchase totals =	$1,039.40		$1,117.8876	$1,117.89	$1,117.90	$1,118.00