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	$31.92	4.652%	$33.4049	$33.40	$33.40	$33.40
Purchase #2	$144.88	5.424%	$152.7383	$152.74	$152.75	$152.70
Purchase #3	$27.51	4.601%	$28.7757	$28.78	$28.80	$28.80
Purchase #4	$152.85	5.144%	$160.7126	$160.71	$160.70	$160.70
Purchase #5	$72.78	10.652%	$80.5325	$80.53	$80.55	$80.50
Purchase #6	$211.32	5.365%	$222.6573	$222.66	$222.65	$222.70
Purchase #7	$174.80	13.368%	$198.1673	$198.17	$198.15	$198.20
7 purchase totals =	$816.06		$876.9886	$876.99	$877.00	$877.00