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	$189.75	12.643%	$213.7401	$213.74	$213.75	$213.70
Purchase #2	$84.90	5.535%	$89.5992	$89.60	$89.60	$89.60
Purchase #3	$72.58	7.719%	$78.1825	$78.18	$78.20	$78.20
Purchase #4	$150.53	3.663%	$156.0439	$156.04	$156.05	$156.00
Purchase #5	$238.97	7.231%	$256.2499	$256.25	$256.25	$256.20
Purchase #6	$207.28	7.401%	$222.6208	$222.62	$222.60	$222.60
Purchase #7	$159.40	7.500%	$171.355	$171.36	$171.35	$171.40
7 purchase totals =	$1,103.41		$1,187.7914	$1,187.79	$1,187.80	$1,187.70