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	$168.49	7.874%	$181.7569	$181.76	$181.75	$181.80
Purchase #2	$138.54	4.284%	$144.4751	$144.48	$144.50	$144.50
Purchase #3	$84.33	6.847%	$90.1041	$90.10	$90.10	$90.10
Purchase #4	$203.77	3.334%	$210.5637	$210.56	$210.55	$210.60
Purchase #5	$135.71	7.384%	$145.7308	$145.73	$145.75	$145.70
Purchase #6	$87.44	12.796%	$98.6288	$98.63	$98.65	$98.60
Purchase #7	$165.61	12.198%	$185.8111	$185.81	$185.80	$185.80
7 purchase totals =	$983.89		$1,057.0705	$1,057.07	$1,057.10	$1,057.10