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	$107.47	4.351%	$112.146	$112.15	$112.15	$112.10
Purchase #2	$53.82	11.746%	$60.1417	$60.14	$60.15	$60.10
Purchase #3	$37.75	13.296%	$42.7692	$42.77	$42.75	$42.80
Purchase #4	$39.82	12.375%	$44.7477	$44.75	$44.75	$44.70
Purchase #5	$198.58	4.205%	$206.9303	$206.93	$206.95	$206.90
Purchase #6	$53.31	12.519%	$59.9839	$59.98	$60.00	$60.00
Purchase #7	$152.96	13.654%	$173.8452	$173.85	$173.85	$173.80
7 purchase totals =	$643.71		$700.5640	$700.57	$700.60	$700.40