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	$78.41	11.612%	$87.515	$87.52	$87.50	$87.50
Purchase #2	$200.98	7.244%	$215.539	$215.54	$215.55	$215.50
Purchase #3	$120.88	5.308%	$127.2963	$127.30	$127.30	$127.30
Purchase #4	$109.69	4.301%	$114.4078	$114.41	$114.40	$114.40
Purchase #5	$114.95	7.774%	$123.8862	$123.89	$123.90	$123.90
Purchase #6	$153.61	13.809%	$174.822	$174.82	$174.80	$174.80
Purchase #7	$87.30	5.435%	$92.0448	$92.04	$92.05	$92.00
7 purchase totals =	$865.82		$935.5111	$935.52	$935.50	$935.40