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	$92.87	7.160%	$99.5195	$99.52	$99.50	$99.50
Purchase #2	$94.31	10.615%	$104.321	$104.32	$104.30	$104.30
Purchase #3	$68.41	6.329%	$72.7397	$72.74	$72.75	$72.70
Purchase #4	$53.44	3.299%	$55.203	$55.20	$55.20	$55.20
Purchase #5	$151.95	10.577%	$168.0218	$168.02	$168.00	$168.00
Purchase #6	$38.56	9.853%	$42.3593	$42.36	$42.35	$42.40
Purchase #7	$170.74	10.712%	$189.0297	$189.03	$189.05	$189.00
7 purchase totals =	$670.28		$731.1940	$731.19	$731.15	$731.10