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	$138.64	6.739%	$147.9829	$147.98	$148.00	$148.00
Purchase #2	$200.73	3.196%	$207.1453	$207.15	$207.15	$207.10
Purchase #3	$105.63	7.564%	$113.6199	$113.62	$113.60	$113.60
Purchase #4	$86.47	3.697%	$89.6668	$89.67	$89.65	$89.70
Purchase #5	$168.50	10.281%	$185.8235	$185.82	$185.80	$185.80
Purchase #6	$18.93	7.602%	$20.3691	$20.37	$20.35	$20.40
Purchase #7	$247.96	5.704%	$262.1036	$262.10	$262.10	$262.10
7 purchase totals =	$966.86		$1,026.7111	$1,026.71	$1,026.65	$1,026.70