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	$134.95	7.555%	$145.1455	$145.15	$145.15	$145.10
Purchase #2	$167.55	10.660%	$185.4108	$185.41	$185.40	$185.40
Purchase #3	$77.48	3.651%	$80.3088	$80.31	$80.30	$80.30
Purchase #4	$36.27	9.479%	$39.708	$39.71	$39.70	$39.70
Purchase #5	$56.76	4.511%	$59.3204	$59.32	$59.30	$59.30
Purchase #6	$235.49	11.853%	$263.4026	$263.40	$263.40	$263.40
Purchase #7	$165.29	9.709%	$181.338	$181.34	$181.35	$181.30
7 purchase totals =	$873.79		$954.6341	$954.64	$954.60	$954.50