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	$108.62	13.231%	$122.9915	$122.99	$123.00	$123.00
Purchase #2	$163.65	4.548%	$171.0928	$171.09	$171.10	$171.10
Purchase #3	$82.82	3.419%	$85.6516	$85.65	$85.65	$85.70
Purchase #4	$96.62	3.477%	$99.9795	$99.98	$100.00	$100.00
Purchase #5	$52.32	4.270%	$54.5541	$54.55	$54.55	$54.60
Purchase #6	$119.36	6.630%	$127.2736	$127.27	$127.25	$127.30
Purchase #7	$137.40	10.188%	$151.3983	$151.40	$151.40	$151.40
7 purchase totals =	$760.79		$812.9414	$812.93	$812.95	$813.10