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	$178.60	10.114%	$196.6636	$196.66	$196.65	$196.70
Purchase #2	$211.44	13.489%	$239.9611	$239.96	$239.95	$240.00
Purchase #3	$80.63	7.335%	$86.5442	$86.54	$86.55	$86.50
Purchase #4	$12.43	5.340%	$13.0938	$13.09	$13.10	$13.10
Purchase #5	$101.89	7.399%	$109.4288	$109.43	$109.45	$109.40
Purchase #6	$189.82	7.635%	$204.3128	$204.31	$204.30	$204.30
Purchase #7	$165.28	7.792%	$178.1586	$178.16	$178.15	$178.20
7 purchase totals =	$940.09		$1,028.1629	$1,028.15	$1,028.15	$1,028.20