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	$145.44	8.529%	$157.8446	$157.84	$157.85	$157.80
Purchase #2	$173.88	9.836%	$190.9828	$190.98	$191.00	$191.00
Purchase #3	$17.82	13.737%	$20.2679	$20.27	$20.25	$20.30
Purchase #4	$36.83	13.736%	$41.889	$41.89	$41.90	$41.90
Purchase #5	$70.69	10.728%	$78.2736	$78.27	$78.25	$78.30
Purchase #6	$80.83	13.647%	$91.8609	$91.86	$91.85	$91.90
Purchase #7	$164.93	12.375%	$185.3401	$185.34	$185.35	$185.30
7 purchase totals =	$690.42		$766.4589	$766.45	$766.45	$766.50