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	$168.67	12.870%	$190.3778	$190.38	$190.40	$190.40
Purchase #2	$152.27	10.393%	$168.0954	$168.10	$168.10	$168.10
Purchase #3	$55.25	7.758%	$59.5363	$59.54	$59.55	$59.50
Purchase #4	$187.96	3.705%	$194.9239	$194.92	$194.90	$194.90
Purchase #5	$82.66	8.851%	$89.9762	$89.98	$90.00	$90.00
Purchase #6	$96.94	6.628%	$103.3652	$103.37	$103.35	$103.40
Purchase #7	$206.41	8.625%	$224.2129	$224.21	$224.20	$224.20
7 purchase totals =	$950.16		$1,030.4877	$1,030.50	$1,030.50	$1,030.50