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	$36.37	3.579%	$37.6717	$37.67	$37.65	$37.70
Purchase #2	$227.62	4.227%	$237.2415	$237.24	$237.25	$237.20
Purchase #3	$52.56	4.690%	$55.0251	$55.03	$55.05	$55.00
Purchase #4	$67.96	6.338%	$72.2673	$72.27	$72.25	$72.30
Purchase #5	$99.68	6.692%	$106.3506	$106.35	$106.35	$106.40
Purchase #6	$42.85	9.332%	$46.8488	$46.85	$46.85	$46.80
Purchase #7	$166.84	9.579%	$182.8216	$182.82	$182.80	$182.80
7 purchase totals =	$693.88		$738.2266	$738.23	$738.20	$738.20