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	$181.66	5.586%	$191.8075	$191.81	$191.80	$191.80
Purchase #2	$40.99	3.678%	$42.4976	$42.50	$42.50	$42.50
Purchase #3	$168.50	11.573%	$188.0005	$188.00	$188.00	$188.00
Purchase #4	$169.27	7.359%	$181.7266	$181.73	$181.75	$181.70
Purchase #5	$197.76	12.209%	$221.9045	$221.90	$221.90	$221.90
Purchase #6	$163.30	5.612%	$172.4644	$172.46	$172.45	$172.50
Purchase #7	$150.69	10.820%	$166.9947	$166.99	$167.00	$167.00
7 purchase totals =	$1,072.17		$1,165.3958	$1,165.39	$1,165.40	$1,165.40