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	$148.84	5.691%	$157.3105	$157.31	$157.30	$157.30
Purchase #2	$56.63	10.551%	$62.605	$62.61	$62.60	$62.60
Purchase #3	$126.64	5.158%	$133.1721	$133.17	$133.15	$133.20
Purchase #4	$69.35	4.150%	$72.228	$72.23	$72.25	$72.20
Purchase #5	$35.84	4.327%	$37.3908	$37.39	$37.40	$37.40
Purchase #6	$151.82	6.846%	$162.2136	$162.21	$162.20	$162.20
Purchase #7	$186.39	4.370%	$194.5352	$194.54	$194.55	$194.50
7 purchase totals =	$775.51		$819.4552	$819.46	$819.45	$819.40