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	$223.57	9.857%	$245.6073	$245.61	$245.60	$245.60
Purchase #2	$161.70	10.560%	$178.7755	$178.78	$178.80	$178.80
Purchase #3	$147.40	11.728%	$164.6871	$164.69	$164.70	$164.70
Purchase #4	$87.77	3.187%	$90.5672	$90.57	$90.55	$90.60
Purchase #5	$45.68	3.114%	$47.1025	$47.10	$47.10	$47.10
Purchase #6	$181.66	8.272%	$196.6869	$196.69	$196.70	$196.70
Purchase #7	$68.97	12.399%	$77.5216	$77.52	$77.50	$77.50
7 purchase totals =	$916.75		$1,000.9481	$1,000.96	$1,000.95	$1,001.00