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	$167.70	11.849%	$187.5708	$187.57	$187.55	$187.60
Purchase #2	$58.93	3.813%	$61.177	$61.18	$61.20	$61.20
Purchase #3	$83.32	7.205%	$89.3232	$89.32	$89.30	$89.30
Purchase #4	$165.57	13.494%	$187.912	$187.91	$187.90	$187.90
Purchase #5	$54.56	13.212%	$61.7685	$61.77	$61.75	$61.80
Purchase #6	$71.76	5.667%	$75.8266	$75.83	$75.85	$75.80
Purchase #7	$109.47	13.180%	$123.8981	$123.90	$123.90	$123.90
7 purchase totals =	$711.31		$787.4762	$787.48	$787.45	$787.50