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	$112.55	4.614%	$117.7431	$117.74	$117.75	$117.70
Purchase #2	$107.39	3.773%	$111.4418	$111.44	$111.45	$111.40
Purchase #3	$208.56	4.783%	$218.5354	$218.54	$218.55	$218.50
Purchase #4	$67.81	5.870%	$71.7904	$71.79	$71.80	$71.80
Purchase #5	$215.81	3.734%	$223.8683	$223.87	$223.85	$223.90
Purchase #6	$220.30	8.206%	$238.3778	$238.38	$238.40	$238.40
Purchase #7	$168.67	13.685%	$191.7525	$191.75	$191.75	$191.80
7 purchase totals =	$1,101.09		$1,173.5093	$1,173.51	$1,173.55	$1,173.50