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	$35.78	4.172%	$37.2727	$37.27	$37.25	$37.30
Purchase #2	$210.83	5.116%	$221.6161	$221.62	$221.60	$221.60
Purchase #3	$90.77	11.460%	$101.1722	$101.17	$101.15	$101.20
Purchase #4	$189.30	10.699%	$209.5532	$209.55	$209.55	$209.60
Purchase #5	$178.77	9.843%	$196.3663	$196.37	$196.35	$196.40
Purchase #6	$227.82	5.591%	$240.5574	$240.56	$240.55	$240.60
Purchase #7	$65.98	3.423%	$68.2385	$68.24	$68.25	$68.20
7 purchase totals =	$999.25		$1,074.7764	$1,074.78	$1,074.70	$1,074.90