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	$53.55	10.818%	$59.343	$59.34	$59.35	$59.30
Purchase #2	$112.92	12.678%	$127.236	$127.24	$127.25	$127.20
Purchase #3	$116.77	3.491%	$120.8464	$120.85	$120.85	$120.80
Purchase #4	$134.59	10.514%	$148.7408	$148.74	$148.75	$148.70
Purchase #5	$106.78	6.801%	$114.0421	$114.04	$114.05	$114.00
Purchase #6	$160.75	3.395%	$166.2075	$166.21	$166.20	$166.20
Purchase #7	$178.31	5.683%	$188.4434	$188.44	$188.45	$188.40
7 purchase totals =	$863.67		$924.8592	$924.86	$924.90	$924.60