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	$94.94	11.525%	$105.8818	$105.88	$105.90	$105.90
Purchase #2	$134.75	7.199%	$144.4507	$144.45	$144.45	$144.50
Purchase #3	$157.59	10.449%	$174.0566	$174.06	$174.05	$174.10
Purchase #4	$73.60	12.397%	$82.7242	$82.72	$82.70	$82.70
Purchase #5	$212.50	11.111%	$236.1109	$236.11	$236.10	$236.10
Purchase #6	$5.73	10.736%	$6.3452	$6.35	$6.35	$6.30
Purchase #7	$144.68	10.524%	$159.9061	$159.91	$159.90	$159.90
7 purchase totals =	$823.79		$909.4755	$909.48	$909.45	$909.50