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	$68.90	3.632%	$71.4024	$71.40	$71.40	$71.40
Purchase #2	$17.69	12.517%	$19.9043	$19.90	$19.90	$19.90
Purchase #3	$169.83	9.474%	$185.9197	$185.92	$185.90	$185.90
Purchase #4	$128.37	7.368%	$137.8283	$137.83	$137.85	$137.80
Purchase #5	$33.65	10.474%	$37.1745	$37.17	$37.15	$37.20
Purchase #6	$100.97	4.214%	$105.2249	$105.22	$105.20	$105.20
Purchase #7	$193.99	5.593%	$204.8399	$204.84	$204.85	$204.80
7 purchase totals =	$713.40		$762.2940	$762.28	$762.25	$762.20