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	$202.28	10.869%	$224.2658	$224.27	$224.25	$224.30
Purchase #2	$88.57	3.867%	$91.995	$92.00	$92.00	$92.00
Purchase #3	$65.47	10.365%	$72.256	$72.26	$72.25	$72.30
Purchase #4	$73.47	6.116%	$77.9634	$77.96	$77.95	$78.00
Purchase #5	$12.91	8.152%	$13.9624	$13.96	$13.95	$14.00
Purchase #6	$64.83	4.728%	$67.8952	$67.90	$67.90	$67.90
Purchase #7	$71.87	9.775%	$78.8953	$78.90	$78.90	$78.90
7 purchase totals =	$579.40		$627.2331	$627.25	$627.20	$627.40