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	$104.57	6.627%	$111.4999	$111.50	$111.50	$111.50
Purchase #2	$225.67	12.295%	$253.4161	$253.42	$253.40	$253.40
Purchase #3	$87.87	12.803%	$99.12	$99.12	$99.10	$99.10
Purchase #4	$183.83	9.595%	$201.4685	$201.47	$201.45	$201.50
Purchase #5	$186.73	4.110%	$194.4046	$194.40	$194.40	$194.40
Purchase #6	$90.56	4.144%	$94.3128	$94.31	$94.30	$94.30
Purchase #7	$188.42	12.611%	$212.1816	$212.18	$212.20	$212.20
7 purchase totals =	$1,067.65		$1,166.4035	$1,166.40	$1,166.35	$1,166.40