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	$146.79	3.769%	$152.3225	$152.32	$152.30	$152.30
Purchase #2	$121.98	7.560%	$131.2017	$131.20	$131.20	$131.20
Purchase #3	$156.33	12.211%	$175.4195	$175.42	$175.40	$175.40
Purchase #4	$189.97	13.348%	$215.3272	$215.33	$215.35	$215.30
Purchase #5	$67.92	13.104%	$76.8202	$76.82	$76.80	$76.80
Purchase #6	$43.50	6.797%	$46.4567	$46.46	$46.45	$46.50
Purchase #7	$222.76	9.402%	$243.7039	$243.70	$243.70	$243.70
7 purchase totals =	$949.25		$1,041.2517	$1,041.25	$1,041.20	$1,041.20