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	$164.65	4.602%	$172.2272	$172.23	$172.25	$172.20
Purchase #2	$91.88	12.467%	$103.3347	$103.33	$103.35	$103.30
Purchase #3	$164.69	11.284%	$183.2736	$183.27	$183.25	$183.30
Purchase #4	$221.50	11.199%	$246.3058	$246.31	$246.30	$246.30
Purchase #5	$67.47	7.783%	$72.7212	$72.72	$72.70	$72.70
Purchase #6	$177.88	4.591%	$186.0465	$186.05	$186.05	$186.00
Purchase #7	$228.79	9.372%	$250.2322	$250.23	$250.25	$250.20
7 purchase totals =	$1,116.86		$1,214.1412	$1,214.14	$1,214.15	$1,214.00