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	$73.57	6.449%	$78.3145	$78.31	$78.30	$78.30
Purchase #2	$86.57	7.770%	$93.2965	$93.30	$93.30	$93.30
Purchase #3	$207.74	3.360%	$214.7201	$214.72	$214.70	$214.70
Purchase #4	$162.59	5.741%	$171.9243	$171.92	$171.90	$171.90
Purchase #5	$187.48	4.523%	$195.9597	$195.96	$195.95	$196.00
Purchase #6	$221.67	9.428%	$242.569	$242.57	$242.55	$242.60
Purchase #7	$83.32	3.780%	$86.4695	$86.47	$86.45	$86.50
7 purchase totals =	$1,022.94		$1,083.2536	$1,083.25	$1,083.15	$1,083.30