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	$152.98	12.659%	$172.3457	$172.35	$172.35	$172.30
Purchase #2	$65.50	9.353%	$71.6262	$71.63	$71.65	$71.60
Purchase #3	$168.50	6.133%	$178.8341	$178.83	$178.85	$178.80
Purchase #4	$145.38	4.849%	$152.4295	$152.43	$152.45	$152.40
Purchase #5	$183.36	6.758%	$195.7515	$195.75	$195.75	$195.80
Purchase #6	$88.87	12.434%	$99.9201	$99.92	$99.90	$99.90
Purchase #7	$117.55	6.874%	$125.6304	$125.63	$125.65	$125.60
7 purchase totals =	$922.14		$996.5375	$996.54	$996.60	$996.40