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	$157.73	10.352%	$174.0582	$174.06	$174.05	$174.10
Purchase #2	$160.59	4.156%	$167.2641	$167.26	$167.25	$167.30
Purchase #3	$123.92	6.355%	$131.7951	$131.80	$131.80	$131.80
Purchase #4	$24.81	10.359%	$27.3801	$27.38	$27.40	$27.40
Purchase #5	$227.85	12.174%	$255.5885	$255.59	$255.60	$255.60
Purchase #6	$143.50	9.625%	$157.3119	$157.31	$157.30	$157.30
Purchase #7	$84.57	5.312%	$89.0624	$89.06	$89.05	$89.10
7 purchase totals =	$922.97		$1,002.4603	$1,002.46	$1,002.45	$1,002.60