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	$174.78	5.864%	$185.0291	$185.03	$185.05	$185.00
Purchase #2	$104.35	7.714%	$112.3996	$112.40	$112.40	$112.40
Purchase #3	$49.99	3.494%	$51.7367	$51.74	$51.75	$51.70
Purchase #4	$177.43	10.637%	$196.3032	$196.30	$196.30	$196.30
Purchase #5	$57.54	3.321%	$59.4509	$59.45	$59.45	$59.50
Purchase #6	$115.92	10.749%	$128.3802	$128.38	$128.40	$128.40
Purchase #7	$53.98	8.254%	$58.4355	$58.44	$58.45	$58.40
7 purchase totals =	$733.99		$791.7352	$791.74	$791.80	$791.70