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	$156.56	11.372%	$174.364	$174.36	$174.35	$174.40
Purchase #2	$52.73	13.309%	$59.7478	$59.75	$59.75	$59.70
Purchase #3	$30.62	9.705%	$33.5917	$33.59	$33.60	$33.60
Purchase #4	$241.63	13.339%	$273.861	$273.86	$273.85	$273.90
Purchase #5	$44.64	10.790%	$49.4567	$49.46	$49.45	$49.50
Purchase #6	$98.72	3.199%	$101.8781	$101.88	$101.90	$101.90
Purchase #7	$42.51	9.386%	$46.5	$46.50	$46.50	$46.50
7 purchase totals =	$667.41		$739.3993	$739.40	$739.40	$739.50