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	$106.94	7.821%	$115.3038	$115.30	$115.30	$115.30
Purchase #2	$58.50	6.837%	$62.4996	$62.50	$62.50	$62.50
Purchase #3	$32.65	12.127%	$36.6095	$36.61	$36.60	$36.60
Purchase #4	$93.65	13.103%	$105.921	$105.92	$105.90	$105.90
Purchase #5	$146.36	10.865%	$162.262	$162.26	$162.25	$162.30
Purchase #6	$99.61	10.369%	$109.9386	$109.94	$109.95	$109.90
Purchase #7	$21.98	6.497%	$23.408	$23.41	$23.40	$23.40
7 purchase totals =	$559.69		$615.9425	$615.94	$615.90	$615.90