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	$152.45	13.268%	$172.6771	$172.68	$172.70	$172.70
Purchase #2	$79.72	5.304%	$83.9483	$83.95	$83.95	$83.90
Purchase #3	$31.29	3.291%	$32.3198	$32.32	$32.30	$32.30
Purchase #4	$110.99	5.809%	$117.4374	$117.44	$117.45	$117.40
Purchase #5	$11.74	13.422%	$13.3157	$13.32	$13.30	$13.30
Purchase #6	$170.65	4.550%	$178.4146	$178.41	$178.40	$178.40
Purchase #7	$114.30	7.715%	$123.1182	$123.12	$123.10	$123.10
7 purchase totals =	$671.14		$721.2311	$721.24	$721.20	$721.10