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	$169.86	5.712%	$179.5624	$179.56	$179.55	$179.60
Purchase #2	$185.70	4.643%	$194.3221	$194.32	$194.30	$194.30
Purchase #3	$18.34	11.267%	$20.4064	$20.41	$20.40	$20.40
Purchase #4	$202.93	7.413%	$217.9732	$217.97	$217.95	$218.00
Purchase #5	$73.45	5.534%	$77.5147	$77.51	$77.50	$77.50
Purchase #6	$210.26	5.470%	$221.7612	$221.76	$221.75	$221.80
Purchase #7	$101.52	4.306%	$105.8915	$105.89	$105.90	$105.90
7 purchase totals =	$962.06		$1,017.4315	$1,017.42	$1,017.35	$1,017.50