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	$10.69	6.685%	$11.4046	$11.40	$11.40	$11.40
Purchase #2	$31.25	13.298%	$35.4056	$35.41	$35.40	$35.40
Purchase #3	$54.25	5.119%	$57.0271	$57.03	$57.05	$57.00
Purchase #4	$35.55	4.829%	$37.2667	$37.27	$37.25	$37.30
Purchase #5	$130.56	4.659%	$136.6428	$136.64	$136.65	$136.60
Purchase #6	$48.31	10.488%	$53.3768	$53.38	$53.40	$53.40
Purchase #7	$33.89	3.255%	$34.9931	$34.99	$35.00	$35.00
7 purchase totals =	$344.50		$366.1167	$366.12	$366.15	$366.10