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	$236.54	4.415%	$246.9832	$246.98	$247.00	$247.00
Purchase #2	$208.59	3.360%	$215.5986	$215.60	$215.60	$215.60
Purchase #3	$73.69	12.684%	$83.0368	$83.04	$83.05	$83.00
Purchase #4	$178.54	11.572%	$199.2006	$199.20	$199.20	$199.20
Purchase #5	$101.62	7.495%	$109.2364	$109.24	$109.25	$109.20
Purchase #6	$196.66	11.378%	$219.036	$219.04	$219.05	$219.00
Purchase #7	$94.90	4.730%	$99.3888	$99.39	$99.40	$99.40
7 purchase totals =	$1,090.54		$1,172.4804	$1,172.49	$1,172.55	$1,172.40