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	$55.83	11.229%	$62.0992	$62.10	$62.10	$62.10
Purchase #2	$170.90	12.424%	$192.1326	$192.13	$192.15	$192.10
Purchase #3	$215.76	3.372%	$223.0354	$223.04	$223.05	$223.00
Purchase #4	$112.37	9.618%	$123.1777	$123.18	$123.20	$123.20
Purchase #5	$50.44	6.178%	$53.5562	$53.56	$53.55	$53.60
Purchase #6	$194.27	8.431%	$210.6489	$210.65	$210.65	$210.60
Purchase #7	$18.78	9.508%	$20.5656	$20.57	$20.55	$20.60
7 purchase totals =	$818.35		$885.2156	$885.23	$885.25	$885.20