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	$185.91	5.458%	$196.057	$196.06	$196.05	$196.10
Purchase #2	$246.91	6.862%	$263.853	$263.85	$263.85	$263.90
Purchase #3	$183.91	8.855%	$200.1952	$200.20	$200.20	$200.20
Purchase #4	$67.69	3.270%	$69.9035	$69.90	$69.90	$69.90
Purchase #5	$96.34	7.200%	$103.2765	$103.28	$103.30	$103.30
Purchase #6	$7.73	4.674%	$8.0913	$8.09	$8.10	$8.10
Purchase #7	$76.79	7.444%	$82.5062	$82.51	$82.50	$82.50
7 purchase totals =	$865.28		$923.8827	$923.89	$923.90	$924.00