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	$140.73	3.680%	$145.9089	$145.91	$145.90	$145.90
Purchase #2	$54.54	13.403%	$61.85	$61.85	$61.85	$61.90
Purchase #3	$83.87	7.160%	$89.8751	$89.88	$89.90	$89.90
Purchase #4	$17.48	9.862%	$19.2039	$19.20	$19.20	$19.20
Purchase #5	$31.74	9.837%	$34.8623	$34.86	$34.85	$34.90
Purchase #6	$88.39	9.293%	$96.6041	$96.60	$96.60	$96.60
Purchase #7	$193.25	7.187%	$207.1389	$207.14	$207.15	$207.10
7 purchase totals =	$610.00		$655.4432	$655.44	$655.45	$655.50