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	$237.77	4.272%	$247.9275	$247.93	$247.95	$247.90
Purchase #2	$156.48	5.268%	$164.7234	$164.72	$164.70	$164.70
Purchase #3	$179.96	9.346%	$196.7791	$196.78	$196.80	$196.80
Purchase #4	$212.47	3.718%	$220.3696	$220.37	$220.35	$220.40
Purchase #5	$165.85	3.457%	$171.5834	$171.58	$171.60	$171.60
Purchase #6	$57.40	4.375%	$59.9113	$59.91	$59.90	$59.90
Purchase #7	$213.81	6.744%	$228.2293	$228.23	$228.25	$228.20
7 purchase totals =	$1,223.74		$1,289.5236	$1,289.52	$1,289.55	$1,289.50