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	$127.63	13.426%	$144.7656	$144.77	$144.75	$144.80
Purchase #2	$72.65	7.563%	$78.1445	$78.14	$78.15	$78.10
Purchase #3	$17.95	3.538%	$18.5851	$18.59	$18.60	$18.60
Purchase #4	$183.27	3.158%	$189.0577	$189.06	$189.05	$189.10
Purchase #5	$53.68	11.348%	$59.7716	$59.77	$59.75	$59.80
Purchase #6	$182.91	10.518%	$202.1485	$202.15	$202.15	$202.10
Purchase #7	$18.64	3.369%	$19.268	$19.27	$19.25	$19.30
7 purchase totals =	$656.73		$711.7410	$711.75	$711.70	$711.80