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	$198.32	12.512%	$223.1338	$223.13	$223.15	$223.10
Purchase #2	$30.50	12.368%	$34.2722	$34.27	$34.25	$34.30
Purchase #3	$25.71	6.866%	$27.4752	$27.48	$27.50	$27.50
Purchase #4	$194.89	12.825%	$219.8846	$219.88	$219.90	$219.90
Purchase #5	$239.76	6.654%	$255.7136	$255.71	$255.70	$255.70
Purchase #6	$55.64	12.834%	$62.7808	$62.78	$62.80	$62.80
Purchase #7	$142.92	8.739%	$155.4098	$155.41	$155.40	$155.40
7 purchase totals =	$887.74		$978.6700	$978.66	$978.70	$978.70