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	$103.72	8.677%	$112.7198	$112.72	$112.70	$112.70
Purchase #2	$55.95	7.777%	$60.3012	$60.30	$60.30	$60.30
Purchase #3	$50.45	11.111%	$56.0555	$56.06	$56.05	$56.10
Purchase #4	$45.38	11.423%	$50.5638	$50.56	$50.55	$50.60
Purchase #5	$100.48	10.694%	$111.2253	$111.23	$111.25	$111.20
Purchase #6	$25.84	12.704%	$29.1227	$29.12	$29.10	$29.10
Purchase #7	$167.76	8.166%	$181.4593	$181.46	$181.45	$181.50
7 purchase totals =	$549.58		$601.4476	$601.45	$601.40	$601.50