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	$187.82	12.294%	$210.9106	$210.91	$210.90	$210.90
Purchase #2	$66.45	8.796%	$72.2949	$72.29	$72.30	$72.30
Purchase #3	$156.55	5.637%	$165.3747	$165.37	$165.35	$165.40
Purchase #4	$37.28	12.813%	$42.0567	$42.06	$42.05	$42.10
Purchase #5	$241.75	3.421%	$250.0203	$250.02	$250.00	$250.00
Purchase #6	$237.45	13.328%	$269.0973	$269.10	$269.10	$269.10
Purchase #7	$46.57	13.514%	$52.8635	$52.86	$52.85	$52.90
7 purchase totals =	$973.87		$1,062.6180	$1,062.61	$1,062.55	$1,062.70