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	$233.27	5.847%	$246.9093	$246.91	$246.90	$246.90
Purchase #2	$88.98	11.609%	$99.3097	$99.31	$99.30	$99.30
Purchase #3	$247.37	9.177%	$270.0711	$270.07	$270.05	$270.10
Purchase #4	$54.48	4.637%	$57.0062	$57.01	$57.00	$57.00
Purchase #5	$163.29	13.453%	$185.2574	$185.26	$185.25	$185.30
Purchase #6	$80.35	4.308%	$83.8115	$83.81	$83.80	$83.80
Purchase #7	$213.63	13.254%	$241.9445	$241.94	$241.95	$241.90
7 purchase totals =	$1,081.37		$1,184.3097	$1,184.31	$1,184.25	$1,184.30