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	$117.90	10.387%	$130.1463	$130.15	$130.15	$130.10
Purchase #2	$47.64	11.292%	$53.0195	$53.02	$53.00	$53.00
Purchase #3	$48.61	6.332%	$51.688	$51.69	$51.70	$51.70
Purchase #4	$187.29	7.111%	$200.6082	$200.61	$200.60	$200.60
Purchase #5	$161.81	8.179%	$175.0444	$175.04	$175.05	$175.00
Purchase #6	$59.46	11.454%	$66.2705	$66.27	$66.25	$66.30
Purchase #7	$105.32	6.393%	$112.0531	$112.05	$112.05	$112.10
7 purchase totals =	$728.03		$788.8300	$788.83	$788.80	$788.80