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	$202.50	13.695%	$230.2324	$230.23	$230.25	$230.20
Purchase #2	$218.42	12.873%	$246.5372	$246.54	$246.55	$246.50
Purchase #3	$159.66	4.697%	$167.1592	$167.16	$167.15	$167.20
Purchase #4	$151.64	9.350%	$165.8183	$165.82	$165.80	$165.80
Purchase #5	$91.64	13.352%	$103.8758	$103.88	$103.90	$103.90
Purchase #6	$246.59	3.780%	$255.9111	$255.91	$255.90	$255.90
Purchase #7	$48.71	13.853%	$55.4578	$55.46	$55.45	$55.50
7 purchase totals =	$1,119.16		$1,224.9918	$1,225.00	$1,225.00	$1,225.00