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	$199.44	8.108%	$215.6106	$215.61	$215.60	$215.60
Purchase #2	$99.90	3.219%	$103.1158	$103.12	$103.10	$103.10
Purchase #3	$61.79	3.855%	$64.172	$64.17	$64.15	$64.20
Purchase #4	$57.49	8.807%	$62.5531	$62.55	$62.55	$62.60
Purchase #5	$63.90	7.264%	$68.5417	$68.54	$68.55	$68.50
Purchase #6	$61.64	8.784%	$67.0545	$67.05	$67.05	$67.10
Purchase #7	$90.63	4.285%	$94.5135	$94.51	$94.50	$94.50
7 purchase totals =	$634.79		$675.5612	$675.55	$675.50	$675.60