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	$168.54	10.780%	$186.7086	$186.71	$186.70	$186.70
Purchase #2	$117.60	11.437%	$131.0499	$131.05	$131.05	$131.00
Purchase #3	$60.61	11.823%	$67.7759	$67.78	$67.80	$67.80
Purchase #4	$48.98	12.820%	$55.2592	$55.26	$55.25	$55.30
Purchase #5	$162.86	11.204%	$181.1068	$181.11	$181.10	$181.10
Purchase #6	$129.35	10.183%	$142.5217	$142.52	$142.50	$142.50
Purchase #7	$202.48	7.614%	$217.8968	$217.90	$217.90	$217.90
7 purchase totals =	$890.42		$982.3189	$982.33	$982.30	$982.30