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	$227.56	4.569%	$237.9572	$237.96	$237.95	$238.00
Purchase #2	$141.56	11.834%	$158.3122	$158.31	$158.30	$158.30
Purchase #3	$136.45	4.841%	$143.0555	$143.06	$143.05	$143.10
Purchase #4	$93.65	7.249%	$100.4387	$100.44	$100.45	$100.40
Purchase #5	$110.87	6.678%	$118.2739	$118.27	$118.25	$118.30
Purchase #6	$196.74	11.444%	$219.2549	$219.25	$219.25	$219.30
Purchase #7	$249.93	5.849%	$264.5484	$264.55	$264.55	$264.50
7 purchase totals =	$1,156.76		$1,241.8408	$1,241.84	$1,241.80	$1,241.90