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	$175.91	3.306%	$181.7256	$181.73	$181.75	$181.70
Purchase #2	$104.60	9.464%	$114.4993	$114.50	$114.50	$114.50
Purchase #3	$62.86	7.252%	$67.4186	$67.42	$67.40	$67.40
Purchase #4	$211.54	13.543%	$240.1889	$240.19	$240.20	$240.20
Purchase #5	$85.39	5.164%	$89.7995	$89.80	$89.80	$89.80
Purchase #6	$184.67	5.453%	$194.7401	$194.74	$194.75	$194.70
Purchase #7	$115.83	6.224%	$123.0393	$123.04	$123.05	$123.00
7 purchase totals =	$940.80		$1,011.4113	$1,011.42	$1,011.45	$1,011.30