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	$77.46	6.764%	$82.6994	$82.70	$82.70	$82.70
Purchase #2	$179.65	3.839%	$186.5468	$186.55	$186.55	$186.50
Purchase #3	$219.96	10.405%	$242.8468	$242.85	$242.85	$242.80
Purchase #4	$51.39	6.268%	$54.6111	$54.61	$54.60	$54.60
Purchase #5	$247.43	8.772%	$269.1346	$269.13	$269.15	$269.10
Purchase #6	$121.59	3.372%	$125.69	$125.69	$125.70	$125.70
Purchase #7	$60.34	7.632%	$64.9451	$64.95	$64.95	$64.90
7 purchase totals =	$957.82		$1,026.4738	$1,026.48	$1,026.50	$1,026.30