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	$198.67	4.669%	$207.9459	$207.95	$207.95	$207.90
Purchase #2	$80.99	10.121%	$89.187	$89.19	$89.20	$89.20
Purchase #3	$71.98	9.121%	$78.5453	$78.55	$78.55	$78.50
Purchase #4	$88.40	12.352%	$99.3192	$99.32	$99.30	$99.30
Purchase #5	$22.36	9.187%	$24.4142	$24.41	$24.40	$24.40
Purchase #6	$109.73	7.481%	$117.9389	$117.94	$117.95	$117.90
Purchase #7	$91.81	4.856%	$96.2683	$96.27	$96.25	$96.30
7 purchase totals =	$663.94		$713.6188	$713.63	$713.60	$713.50