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	$102.61	7.138%	$109.9343	$109.93	$109.95	$109.90
Purchase #2	$195.67	8.726%	$212.7442	$212.74	$212.75	$212.70
Purchase #3	$35.65	5.118%	$37.4746	$37.47	$37.45	$37.50
Purchase #4	$204.46	9.331%	$223.5382	$223.54	$223.55	$223.50
Purchase #5	$179.76	4.542%	$187.9247	$187.92	$187.90	$187.90
Purchase #6	$87.68	8.744%	$95.3467	$95.35	$95.35	$95.30
Purchase #7	$164.90	4.322%	$172.027	$172.03	$172.05	$172.00
7 purchase totals =	$970.73		$1,038.9897	$1,038.98	$1,039.00	$1,038.80