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	$55.29	10.208%	$60.934	$60.93	$60.95	$60.90
Purchase #2	$91.95	9.735%	$100.9013	$100.90	$100.90	$100.90
Purchase #3	$160.92	6.550%	$171.4603	$171.46	$171.45	$171.50
Purchase #4	$83.76	3.653%	$86.8198	$86.82	$86.80	$86.80
Purchase #5	$62.32	7.532%	$67.0139	$67.01	$67.00	$67.00
Purchase #6	$30.92	3.499%	$32.0019	$32.00	$32.00	$32.00
Purchase #7	$72.42	13.729%	$82.3625	$82.36	$82.35	$82.40
7 purchase totals =	$557.58		$601.4937	$601.48	$601.45	$601.50