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	$173.66	12.857%	$195.9875	$195.99	$196.00	$196.00
Purchase #2	$149.72	8.564%	$162.542	$162.54	$162.55	$162.50
Purchase #3	$99.58	5.700%	$105.2561	$105.26	$105.25	$105.30
Purchase #4	$207.46	7.404%	$222.8203	$222.82	$222.80	$222.80
Purchase #5	$103.86	4.173%	$108.1941	$108.19	$108.20	$108.20
Purchase #6	$221.86	5.173%	$233.3368	$233.34	$233.35	$233.30
Purchase #7	$182.63	7.545%	$196.4094	$196.41	$196.40	$196.40
7 purchase totals =	$1,138.77		$1,224.5462	$1,224.55	$1,224.55	$1,224.50