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	$105.69	13.204%	$119.6453	$119.65	$119.65	$119.60
Purchase #2	$53.76	5.807%	$56.8818	$56.88	$56.90	$56.90
Purchase #3	$161.73	11.316%	$180.0314	$180.03	$180.05	$180.00
Purchase #4	$72.27	3.654%	$74.9107	$74.91	$74.90	$74.90
Purchase #5	$237.58	7.740%	$255.9687	$255.97	$255.95	$256.00
Purchase #6	$137.48	12.782%	$155.0527	$155.05	$155.05	$155.10
Purchase #7	$40.31	4.380%	$42.0756	$42.08	$42.10	$42.10
7 purchase totals =	$808.82		$884.5662	$884.57	$884.60	$884.60