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	$99.26	6.640%	$105.8509	$105.85	$105.85	$105.90
Purchase #2	$118.34	10.804%	$131.1255	$131.13	$131.15	$131.10
Purchase #3	$196.27	13.669%	$223.0981	$223.10	$223.10	$223.10
Purchase #4	$104.32	4.402%	$108.9122	$108.91	$108.90	$108.90
Purchase #5	$183.47	8.867%	$199.7383	$199.74	$199.75	$199.70
Purchase #6	$179.48	12.850%	$202.5432	$202.54	$202.55	$202.50
Purchase #7	$55.31	13.561%	$62.8106	$62.81	$62.80	$62.80
7 purchase totals =	$936.45		$1,034.0788	$1,034.08	$1,034.10	$1,034.00