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	$217.41	4.194%	$226.5282	$226.53	$226.55	$226.50
Purchase #2	$136.28	4.143%	$141.9261	$141.93	$141.95	$141.90
Purchase #3	$75.48	3.803%	$78.3505	$78.35	$78.35	$78.40
Purchase #4	$12.64	11.248%	$14.0617	$14.06	$14.05	$14.10
Purchase #5	$35.73	4.795%	$37.4433	$37.44	$37.45	$37.40
Purchase #6	$232.46	4.608%	$243.1718	$243.17	$243.15	$243.20
Purchase #7	$54.72	7.874%	$59.0287	$59.03	$59.05	$59.00
7 purchase totals =	$764.72		$800.5103	$800.51	$800.55	$800.50