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	$80.90	11.326%	$90.0627	$90.06	$90.05	$90.10
Purchase #2	$136.57	11.591%	$152.3998	$152.40	$152.40	$152.40
Purchase #3	$190.46	12.132%	$213.5666	$213.57	$213.55	$213.60
Purchase #4	$65.83	5.764%	$69.6244	$69.62	$69.60	$69.60
Purchase #5	$92.76	5.383%	$97.7533	$97.75	$97.75	$97.80
Purchase #6	$247.62	4.405%	$258.5277	$258.53	$258.55	$258.50
Purchase #7	$206.31	4.401%	$215.3897	$215.39	$215.40	$215.40
7 purchase totals =	$1,020.45		$1,097.3242	$1,097.32	$1,097.30	$1,097.40