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	$61.98	10.856%	$68.7085	$68.71	$68.70	$68.70
Purchase #2	$51.40	8.428%	$55.732	$55.73	$55.75	$55.70
Purchase #3	$141.30	8.192%	$152.8753	$152.88	$152.90	$152.90
Purchase #4	$223.29	9.863%	$245.3131	$245.31	$245.30	$245.30
Purchase #5	$223.38	3.650%	$231.5334	$231.53	$231.55	$231.50
Purchase #6	$143.85	12.660%	$162.0614	$162.06	$162.05	$162.10
Purchase #7	$79.92	12.152%	$89.6319	$89.63	$89.65	$89.60
7 purchase totals =	$925.12		$1,005.8556	$1,005.85	$1,005.90	$1,005.80