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	$153.26	4.776%	$160.5797	$160.58	$160.60	$160.60
Purchase #2	$198.99	8.746%	$216.3937	$216.39	$216.40	$216.40
Purchase #3	$212.27	7.362%	$227.8973	$227.90	$227.90	$227.90
Purchase #4	$27.88	13.761%	$31.7166	$31.72	$31.70	$31.70
Purchase #5	$80.69	10.429%	$89.1052	$89.11	$89.10	$89.10
Purchase #6	$144.92	12.398%	$162.8872	$162.89	$162.90	$162.90
Purchase #7	$90.91	8.854%	$98.9592	$98.96	$98.95	$99.00
7 purchase totals =	$908.92		$987.5389	$987.55	$987.55	$987.60