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	$88.90	13.479%	$100.8828	$100.88	$100.90	$100.90
Purchase #2	$105.60	3.284%	$109.0679	$109.07	$109.05	$109.10
Purchase #3	$241.38	9.614%	$264.5863	$264.59	$264.60	$264.60
Purchase #4	$147.36	10.339%	$162.5956	$162.60	$162.60	$162.60
Purchase #5	$119.71	12.425%	$134.584	$134.58	$134.60	$134.60
Purchase #6	$222.55	5.408%	$234.5855	$234.59	$234.60	$234.60
Purchase #7	$155.81	8.220%	$168.6176	$168.62	$168.60	$168.60
7 purchase totals =	$1,081.31		$1,174.9197	$1,174.93	$1,174.95	$1,175.00