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	$168.80	7.236%	$181.0144	$181.01	$181.00	$181.00
Purchase #2	$213.68	10.602%	$236.3344	$236.33	$236.35	$236.30
Purchase #3	$29.80	10.405%	$32.9007	$32.90	$32.90	$32.90
Purchase #4	$237.56	7.524%	$255.434	$255.43	$255.45	$255.40
Purchase #5	$57.63	13.274%	$65.2798	$65.28	$65.30	$65.30
Purchase #6	$202.67	10.389%	$223.7254	$223.73	$223.75	$223.70
Purchase #7	$179.68	6.402%	$191.1831	$191.18	$191.20	$191.20
7 purchase totals =	$1,089.82		$1,185.8718	$1,185.86	$1,185.95	$1,185.80