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	$171.76	3.477%	$177.7321	$177.73	$177.75	$177.70
Purchase #2	$243.73	3.205%	$251.5415	$251.54	$251.55	$251.50
Purchase #3	$102.73	13.400%	$116.4958	$116.50	$116.50	$116.50
Purchase #4	$106.28	9.368%	$116.2363	$116.24	$116.25	$116.20
Purchase #5	$179.59	3.229%	$185.389	$185.39	$185.40	$185.40
Purchase #6	$131.51	7.632%	$141.5468	$141.55	$141.55	$141.50
Purchase #7	$104.41	6.663%	$111.3668	$111.37	$111.35	$111.40
7 purchase totals =	$1,040.01		$1,100.3083	$1,100.32	$1,100.35	$1,100.20