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	$5.48	3.790%	$5.6877	$5.69	$5.70	$5.70
Purchase #2	$12.67	5.227%	$13.3323	$13.33	$13.35	$13.30
Purchase #3	$27.82	3.289%	$28.735	$28.74	$28.75	$28.70
Purchase #4	$219.93	9.339%	$240.4693	$240.47	$240.45	$240.50
Purchase #5	$114.33	3.834%	$118.7134	$118.71	$118.70	$118.70
Purchase #6	$184.37	6.793%	$196.8943	$196.89	$196.90	$196.90
Purchase #7	$12.73	5.801%	$13.4685	$13.47	$13.45	$13.50
7 purchase totals =	$577.33		$617.3005	$617.30	$617.30	$617.30