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	$175.82	4.509%	$183.7477	$183.75	$183.75	$183.70
Purchase #2	$77.97	6.180%	$82.7885	$82.79	$82.80	$82.80
Purchase #3	$215.26	6.649%	$229.5726	$229.57	$229.55	$229.60
Purchase #4	$38.58	9.630%	$42.2953	$42.30	$42.30	$42.30
Purchase #5	$129.84	5.794%	$137.3629	$137.36	$137.35	$137.40
Purchase #6	$206.56	7.531%	$222.116	$222.12	$222.10	$222.10
Purchase #7	$151.93	10.490%	$167.8675	$167.87	$167.85	$167.90
7 purchase totals =	$995.96		$1,065.7505	$1,065.76	$1,065.70	$1,065.80