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	$109.30	8.818%	$118.9381	$118.94	$118.95	$118.90
Purchase #2	$6.90	12.413%	$7.7565	$7.76	$7.75	$7.80
Purchase #3	$140.35	7.630%	$151.0587	$151.06	$151.05	$151.10
Purchase #4	$175.44	4.812%	$183.8822	$183.88	$183.90	$183.90
Purchase #5	$169.28	13.798%	$192.6373	$192.64	$192.65	$192.60
Purchase #6	$150.76	13.805%	$171.5724	$171.57	$171.55	$171.60
Purchase #7	$99.25	4.155%	$103.3738	$103.37	$103.35	$103.40
7 purchase totals =	$851.28		$929.2190	$929.22	$929.20	$929.30