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	$234.64	12.665%	$264.3572	$264.36	$264.35	$264.40
Purchase #2	$162.83	13.482%	$184.7827	$184.78	$184.80	$184.80
Purchase #3	$163.50	9.254%	$178.6303	$178.63	$178.65	$178.60
Purchase #4	$238.73	11.713%	$266.6924	$266.69	$266.70	$266.70
Purchase #5	$211.45	8.449%	$229.3154	$229.32	$229.30	$229.30
Purchase #6	$157.74	6.699%	$168.307	$168.31	$168.30	$168.30
Purchase #7	$112.96	13.114%	$127.7736	$127.77	$127.75	$127.80
7 purchase totals =	$1,281.85		$1,419.8586	$1,419.86	$1,419.85	$1,419.90