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	$94.76	4.737%	$99.2488	$99.25	$99.25	$99.20
Purchase #2	$66.66	10.254%	$73.4953	$73.50	$73.50	$73.50
Purchase #3	$44.34	5.827%	$46.9237	$46.92	$46.90	$46.90
Purchase #4	$77.87	6.412%	$82.863	$82.86	$82.85	$82.90
Purchase #5	$89.28	10.183%	$98.3714	$98.37	$98.35	$98.40
Purchase #6	$178.31	5.269%	$187.7052	$187.71	$187.70	$187.70
Purchase #7	$242.98	5.739%	$256.9246	$256.92	$256.90	$256.90
7 purchase totals =	$794.20		$845.5320	$845.53	$845.45	$845.50