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	$131.51	10.617%	$145.4724	$145.47	$145.45	$145.50
Purchase #2	$126.32	8.247%	$136.7376	$136.74	$136.75	$136.70
Purchase #3	$96.35	5.314%	$101.47	$101.47	$101.45	$101.50
Purchase #4	$52.83	6.129%	$56.068	$56.07	$56.05	$56.10
Purchase #5	$47.74	5.716%	$50.4688	$50.47	$50.45	$50.50
Purchase #6	$235.67	13.851%	$268.3127	$268.31	$268.30	$268.30
Purchase #7	$200.27	11.109%	$222.518	$222.52	$222.50	$222.50
7 purchase totals =	$890.69		$981.0475	$981.05	$980.95	$981.10