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	$169.62	7.350%	$182.0871	$182.09	$182.10	$182.10
Purchase #2	$216.67	11.196%	$240.9284	$240.93	$240.95	$240.90
Purchase #3	$192.66	7.598%	$207.2983	$207.30	$207.30	$207.30
Purchase #4	$35.51	9.435%	$38.8604	$38.86	$38.85	$38.90
Purchase #5	$39.45	11.322%	$43.9165	$43.92	$43.90	$43.90
Purchase #6	$212.98	8.786%	$231.6924	$231.69	$231.70	$231.70
Purchase #7	$150.37	10.711%	$166.4761	$166.48	$166.50	$166.50
7 purchase totals =	$1,017.26		$1,111.2592	$1,111.27	$1,111.30	$1,111.30