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	$192.89	4.513%	$201.5951	$201.60	$201.60	$201.60
Purchase #2	$127.82	10.736%	$141.5428	$141.54	$141.55	$141.50
Purchase #3	$222.91	8.809%	$242.5461	$242.55	$242.55	$242.50
Purchase #4	$145.55	8.473%	$157.8825	$157.88	$157.90	$157.90
Purchase #5	$170.25	9.562%	$186.5293	$186.53	$186.55	$186.50
Purchase #6	$88.43	13.791%	$100.6254	$100.63	$100.65	$100.60
Purchase #7	$57.92	13.294%	$65.6199	$65.62	$65.60	$65.60
7 purchase totals =	$1,005.77		$1,096.3411	$1,096.35	$1,096.40	$1,096.20