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	$239.62	11.354%	$266.8265	$266.83	$266.85	$266.80
Purchase #2	$202.48	11.209%	$225.176	$225.18	$225.20	$225.20
Purchase #3	$190.75	3.187%	$196.8292	$196.83	$196.85	$196.80
Purchase #4	$236.45	3.213%	$244.0471	$244.05	$244.05	$244.00
Purchase #5	$104.74	4.169%	$109.1066	$109.11	$109.10	$109.10
Purchase #6	$53.61	10.646%	$59.3173	$59.32	$59.30	$59.30
Purchase #7	$106.80	4.256%	$111.3454	$111.35	$111.35	$111.30
7 purchase totals =	$1,134.45		$1,212.6481	$1,212.67	$1,212.70	$1,212.50