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	$145.75	5.334%	$153.5243	$153.52	$153.50	$153.50
Purchase #2	$142.62	12.697%	$160.7285	$160.73	$160.75	$160.70
Purchase #3	$182.51	4.827%	$191.3198	$191.32	$191.30	$191.30
Purchase #4	$192.28	3.668%	$199.3328	$199.33	$199.35	$199.30
Purchase #5	$101.88	10.493%	$112.5703	$112.57	$112.55	$112.60
Purchase #6	$249.62	6.604%	$266.1049	$266.10	$266.10	$266.10
Purchase #7	$80.78	10.557%	$89.3079	$89.31	$89.30	$89.30
7 purchase totals =	$1,095.44		$1,172.8885	$1,172.88	$1,172.85	$1,172.80