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	$202.26	13.235%	$229.0291	$229.03	$229.05	$229.00
Purchase #2	$166.82	11.410%	$185.8542	$185.85	$185.85	$185.90
Purchase #3	$53.41	6.314%	$56.7823	$56.78	$56.80	$56.80
Purchase #4	$45.59	12.769%	$51.4114	$51.41	$51.40	$51.40
Purchase #5	$130.39	5.265%	$137.255	$137.26	$137.25	$137.30
Purchase #6	$61.25	7.170%	$65.6416	$65.64	$65.65	$65.60
Purchase #7	$66.82	6.301%	$71.0303	$71.03	$71.05	$71.00
7 purchase totals =	$726.54		$797.0039	$797.00	$797.05	$797.00