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	$35.68	5.852%	$37.768	$37.77	$37.75	$37.80
Purchase #2	$225.73	3.328%	$233.2423	$233.24	$233.25	$233.20
Purchase #3	$44.72	9.646%	$49.0337	$49.03	$49.05	$49.00
Purchase #4	$109.69	13.479%	$124.4751	$124.48	$124.50	$124.50
Purchase #5	$69.27	12.667%	$78.0444	$78.04	$78.05	$78.00
Purchase #6	$87.95	9.511%	$96.3149	$96.31	$96.30	$96.30
Purchase #7	$95.89	10.693%	$106.1435	$106.14	$106.15	$106.10
7 purchase totals =	$668.93		$725.0219	$725.01	$725.05	$724.90