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	$175.87	13.294%	$199.2502	$199.25	$199.25	$199.30
Purchase #2	$96.77	5.350%	$101.9472	$101.95	$101.95	$101.90
Purchase #3	$188.69	5.123%	$198.3566	$198.36	$198.35	$198.40
Purchase #4	$123.56	6.466%	$131.5494	$131.55	$131.55	$131.50
Purchase #5	$64.74	12.537%	$72.8565	$72.86	$72.85	$72.90
Purchase #6	$142.57	6.166%	$151.3609	$151.36	$151.35	$151.40
Purchase #7	$33.97	12.686%	$38.2794	$38.28	$38.30	$38.30
7 purchase totals =	$826.17		$893.6002	$893.61	$893.60	$893.70