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	$183.40	13.321%	$207.8307	$207.83	$207.85	$207.80
Purchase #2	$23.56	9.639%	$25.8309	$25.83	$25.85	$25.80
Purchase #3	$228.73	12.124%	$256.4612	$256.46	$256.45	$256.50
Purchase #4	$155.66	4.267%	$162.302	$162.30	$162.30	$162.30
Purchase #5	$198.59	8.723%	$215.913	$215.91	$215.90	$215.90
Purchase #6	$75.83	9.273%	$82.8617	$82.86	$82.85	$82.90
Purchase #7	$88.54	3.723%	$91.8363	$91.84	$91.85	$91.80
7 purchase totals =	$954.31		$1,043.0358	$1,043.03	$1,043.05	$1,043.00