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	$94.82	6.288%	$100.7823	$100.78	$100.80	$100.80
Purchase #2	$104.47	10.425%	$115.361	$115.36	$115.35	$115.40
Purchase #3	$207.54	12.432%	$233.3414	$233.34	$233.35	$233.30
Purchase #4	$172.60	13.772%	$196.3705	$196.37	$196.35	$196.40
Purchase #5	$75.97	3.160%	$78.3707	$78.37	$78.35	$78.40
Purchase #6	$216.40	11.614%	$241.5327	$241.53	$241.55	$241.50
Purchase #7	$204.49	11.755%	$228.5278	$228.53	$228.55	$228.50
7 purchase totals =	$1,076.29		$1,194.2864	$1,194.28	$1,194.30	$1,194.30