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	$174.40	12.486%	$196.1756	$196.18	$196.20	$196.20
Purchase #2	$109.27	12.864%	$123.3265	$123.33	$123.35	$123.30
Purchase #3	$152.79	8.357%	$165.5587	$165.56	$165.55	$165.60
Purchase #4	$196.54	8.395%	$213.0395	$213.04	$213.05	$213.00
Purchase #5	$19.82	7.148%	$21.2367	$21.24	$21.25	$21.20
Purchase #6	$223.54	6.142%	$237.2698	$237.27	$237.25	$237.30
Purchase #7	$73.45	9.628%	$80.5218	$80.52	$80.50	$80.50
7 purchase totals =	$949.81		$1,037.1286	$1,037.14	$1,037.15	$1,037.10