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	$175.52	8.240%	$189.9828	$189.98	$190.00	$190.00
Purchase #2	$105.84	10.604%	$117.0633	$117.06	$117.05	$117.10
Purchase #3	$19.86	7.372%	$21.3241	$21.32	$21.30	$21.30
Purchase #4	$179.72	3.459%	$185.9365	$185.94	$185.95	$185.90
Purchase #5	$197.82	13.709%	$224.9391	$224.94	$224.95	$224.90
Purchase #6	$158.27	4.275%	$165.036	$165.04	$165.05	$165.00
Purchase #7	$214.57	7.256%	$230.1392	$230.14	$230.15	$230.10
7 purchase totals =	$1,051.60		$1,134.4210	$1,134.42	$1,134.45	$1,134.30