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	$125.65	4.305%	$131.0592	$131.06	$131.05	$131.10
Purchase #2	$135.62	4.671%	$141.9548	$141.95	$141.95	$142.00
Purchase #3	$166.34	13.301%	$188.4649	$188.46	$188.45	$188.50
Purchase #4	$151.25	7.693%	$162.8857	$162.89	$162.90	$162.90
Purchase #5	$183.89	4.800%	$192.7167	$192.72	$192.70	$192.70
Purchase #6	$165.71	9.860%	$182.049	$182.05	$182.05	$182.00
Purchase #7	$245.79	10.690%	$272.065	$272.07	$272.05	$272.10
7 purchase totals =	$1,174.25		$1,271.1953	$1,271.20	$1,271.15	$1,271.30