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	$128.63	9.492%	$140.8396	$140.84	$140.85	$140.80
Purchase #2	$139.26	3.177%	$143.6843	$143.68	$143.70	$143.70
Purchase #3	$222.96	9.806%	$244.8235	$244.82	$244.80	$244.80
Purchase #4	$202.99	9.303%	$221.8742	$221.87	$221.85	$221.90
Purchase #5	$67.77	6.736%	$72.335	$72.34	$72.35	$72.30
Purchase #6	$242.92	5.200%	$255.5518	$255.55	$255.55	$255.60
Purchase #7	$79.99	13.274%	$90.6079	$90.61	$90.60	$90.60
7 purchase totals =	$1,084.52		$1,169.7163	$1,169.71	$1,169.70	$1,169.70